SMDF and GGF neuregulin splice variant isoforms and uses thereof

ABSTRACT

Distinct cDNAs encoding six cysteine-rich domain-NRGs and four glial growth factor isoforms were identified and sequenced. Additional heterogeneity is found in the EGF-like (α- and β-isoforms) and carboxy terminal (a and b variant) regions of CRD-NRGs. Furthermore, the predicted GGF proteins contain glycosylation domains previously found only in mesenchymal NRGs. GGF mRNAs accumulate in axotomized nerve, a subpopulation of DRG neurons and most spinal cord motoneurons. CRD-NRGs, however, are undetectable in injured nerve except by RT-PCR. In contrast, the majority of DRG and spinal cord motor neurons express CRD-NRGs, with a β1 isoform being most abundant and at least some of these proteins are secreted in a form capable of activating erbB receptors. Thus, GGF and CRD-NRG subfamilies are more structurally diverse than previously appreciated. NRG actions during Wallerian degeneration may be modulated by the action of distinct splice variants.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional patent application claims benefit of provisional patent application U.S. Ser. No. 60/158,622, filed Oct. 8, 1999, now abandoned.

FEDERAL FUNDING LEGEND

This invention was produced in part using funds from the Federal government under grant no. R01 NS37514. Accordingly, the Federal government has certain rights in this invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the fields of neurobiology and developmental biology. More specifically, the present invention relates to the identification of novel neuregulin splice variant isoforms.

2. Description of the Related Art

Traumatic injury of adult mammalian peripheral nerve results in degeneration of axon segments and myelin distal to the injury site with concomitant Schwann cell dedifferentiation and proliferation. These changes in Schwann cell morphology are essential for subsequent axonal regeneration (Hall and Gregson, 1977; Pellegrino et al., 1986; Fawcett and Keynes, 1990; Nadim et al., 1990) and are accompanied by increased Schwann cell expression of molecules promoting neurite sprouting [e.g., neurotrophic factors and cell adhesion molecules; reviewed in Fawcett and Keynes, 1990; Fu and Gordon, 1997]. The signals responsible for repressing myelin protein synthesis, inducing expression of molecules supportive of axonal regeneration, and stimulating Schwann cell mitogenesis in injured nerve are poorly understood. It is likely, however, that these signaling molecules include several members of the neuregulin (NRG) family of growth and differentiation factors.

The neuregulin (NRG) family of growth and differentiation factors is thought to form a complex network of intercellular signaling molecules mediating multiple important developmental, maintenance and regenerative functions throughout the nervous system. For instance, neuregulins are highly expressed by sensory and motor neurons during development (Chen et al., 1994; Falls et al., 1993; Ho et al., 1995; Marchionni et al., 1993) and have been implicated as axon-derived signals influencing the differentiation, survival and proliferation of associated Schwann cells during this same period (reviewed in (Topilko et al., 1996; Lemke, 1996)). Neuregulins are also highly potent mitogens for neonatal Schwann cells in vitro (Brockes et al., 1980; Goodearl et al., 1993; Levi et al., 1995) and repress expression of myelin protein zero (P₀) and myelin basic protein in these same cells (Cheng and Mudge, 1996). Furthermore, axon-associated NRGs are a component of the “axon-associated mitogen” found on the neurites of neonatal dorsal root ganglion (DRG) neurons (Morrissey et al., 1995). Based on these developmental and in vitro observations, it is hypothesized that neuregulins, potentially released from the injured axon, similarly induce the Schwann cell dedifferentiation and proliferation during the Wallerian degeneration which follows traumatic injury of peripheral nerve and which is essential for subsequent axonal regeneration (Hall and Gregson, 1977; Pellegrino et al., 1986; Fawcett and Keynes, 1990; Nadim et al., 1990).

These molecules are indeed expressed with the temporal and spatial distribution expected for postaxotomy mediators of Schwann cell proliferation and/or other effects in axotomized rat sciatic nerve (Carroll et al., 1997). However, Schwann cells themselves apparently produce neuregulin, a finding consistent with recent reports of neuregulin expression by cultured neonatal Schwann cells in vitro (Raabe et al., 1996; Rosenbaum et al., 1997). Furthermore, the dorsal root ganglia (DRG) sensory and spinal cord motor neurons projecting into the sciatic nerve express the erbB receptors necessary for neuregulin responsiveness during embryogenesis and adulthood. Also, recombinant neuregulin is a survival factor for embryonic day 15 spinal cord motor neurons in vitro. It is therefore likely that neuregulin signaling proceeds bidirectionally between these cell types or that Schwann cell- and neuron-derived neuregulins act in an autocrine fashion.

Since astrocytes, oligodendrocytes and many populations of central nervous system (CNS) neurons similarly express both neuregulins and neuregulin receptors, these same possibilities may need to be considered in the brain. Given the potential complexity of neuregulin signaling among glia and neurons, the question arises as to how neuregulin signaling might be compartmentalized or otherwise regulated. This control may be facilitated, in part, by the synthesis of distinct forms of neuregulin by each expressing cell type. Cloning of neuregulin family members (Wen et al., 1992; Marchionni et al., 1993; Carroll et al., 1997; Falls et al., 1993; Ho et al., 1995; Carroll et al., 1997; Yang et al., 1998) demonstrated these molecules to be structurally diverse proteins translated from alternatively spliced mRNAs transcribed from a single locus. Neuregulins may be divided into three subfamilies, each defined by their unique N terminus and known as the heregulin (HRG)/neu differentiation factor (NDF)/mesenchymal, glial growth factor (GGF) and sensory and motor neuron-derived factor [SMDF; also known as cysteine-rich domain (CRD)-neuregulin] subfamilies.

The structures of various members of the neu differentiation factor subfamily have been thoroughly studied. The seven known neu differentiation factor isoforms are synthesized as either directly secretable forms or as transmembrane precursors requiring proteolytic cleavage for release (Wen et al., 1994). These proteins possess distinct epidermal growth factor (EGF)-like domains (α and β isoforms) resulting in differences in receptor affinity (Wen et al., 1994) and ability to induce biological effects (Marikovsky et al., 1995; Pinkas-Kramarski et al., 1996).

The EGF-like domain, which consists of a common region fused to either α- or β-domains, is essential for biologic activity. Truncated β-neuregulin molecules containing only the EGF-like domain bind to the neuregulin receptor with an affinity similar to that of the full-length factor (Holmes et al., 1992; Peles et al., 1993) and are capable of inducing a variety of biologic responses (Holmes et al., 1992; Peles et al., 1993; Chu et al., 1995; Levi et al., 1995; Syroid et al., 1996).

In spite of their similar structures, neuregulin α and β EGF-like domains are not functionally equivalent; β-neuregulins have an affinity for erbB receptors an order of magnitude greater than α-neuregulins (Wen et al., 1994). Furthermore, α-neuregulins are nonmitogenic for some, but not all, cell types which proliferate in response to β-neuregulins (Pinkas-Kramarski et al., 1996).

Further variability in other regions may alter glycosylation (Wen et al., 1994), protease-mediated release from the cell membrane (Wen et al., 1994) and direct signaling by transmembrane precursors (Wang et al., 1998). In addition to the unique amino termini (the functions of which are currently unknown), the mesenchymal and GGF (but not the SMDF) neuregulin subfamilies contain an immunoglobulin-like domain (Ben-Baruch and Yarden, 1994; Peles and Yarden, 1993; Ho et al., 1995) mediating neuregulin interactions with cell surface glycoproteins, with resultant concentration and specific localization of the factor (Sudhalter et al., 1996). Splice variants in the glial growth factor and mesenchymal neuregulin subfamilies also may contain serine and threonine-rich spacer domains which serve as the site of o- and n-linked glycosylation (Wen et al., 1994; Carroll et al., 1997); this glycosylation is non-essential for biologic activity and the precise function(s) of this region is as yet unknown.

Neuregulins may be synthesized as either transmembrane precursors or directly secretable forms. This distinction depends upon the juxtamembrane domain, which is immediately C terminal to the EGF-like domain. Four juxtamembrane domains, designated 1 to 4, have been identified in the rat. In this regard, the ‘3’ juxtamembrane domain is notable in that it, unlike other juxtamembrane domains, contains a termination codon, thus leading to truncation of the factor and synthesis in a directly secretable form. In all other neuregulin isoforms, the juxtamembrane domain is followed by a transmembrane domain which anchors the factor in the cell membrane and is itself coupled to one of three possible cytoplasmic domains (designated a, b, and c) (Wen et al., 1994). The cytoplasmic domains are highly conserved between species, suggesting an essential function (Wen et al., 1994); indeed, it has been recently reported that neuregulin cytoplasmic domains bind LIM kinase 1, suggesting that neuregulin transmembrane precursors are capable of transmitting signals into the interior of the cell synthesizing these proteins (Wang et al., 1998).

Whether members of the glial growth factor and sensory and motor neuron-derived factor subfamilies demonstrate the same degree of structural diversity described for the NDF subfamily has not yet been determined. It is highly likely that the neuregulin isoforms present in injured peripheral nerve represent a diverse population of previously unknown glial growth factor and sensory and motor neuron-derived factor splice variants. The neuregulins selectively induced in axotomized peripheral nerve coincident with the onset of Schwann cell DNA synthesis belong predominantly to the glial growth factor subfamily, while neuregulins of both the glial growth factor and sensory and motor neuron-derived factor subfamilies are expressed in DRG and spinal cord (Carroll et al., 1997).

The prior art is deficient in the lack of knowledge about the sensory and motor neuron-derived factor (SMDF) and glial growth factor (GGF) neuregulin splice variants expressed in the nervous system. The present invention fulfills this longstanding need and desire in the art.

SUMMARY OF THE INVENTION

Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention. These embodiments are given for the purpose of disclosure.

Reverse transcription-polymerase chain reaction (RT-PCR) analyses suggest that axotomized sciatic nerve, DRG and spinal cord all contain complex mixtures of neuregulin isoforms, potentially representing a large number of previously undescribed splice variants with novel functional characteristics. Consequently, an exhaustive cloning approach was used to identify the neuregulin isoforms expressed in surgically transected rat sciatic nerve, postaxotomy lumbar dorsal root ganglia, postaxotomy lumbar spinal cord and JS1 schwannoma cells, a rat line mimicking at least some characteristics of primary cultures of neonatal rat Schwann cells. The structures of cDNAs encoding six SDMF splice variants and four GGF isoforms are described here, representing both directly secreted proteins and transmembrane precursors. These proteins demonstrate extensive structural variability in multiple regions, suggesting they are functionally distinct.

Whether neuregulin isoforms are predominantly expressed in axotomized peripheral nerve and postaxotomy DRG and spinal cord; (2) whether distinct neuronal subpopulations in the latter two tissues express specific neuregulin splice variants; and, (3) what was the distribution of each group of transcripts was examined. In addition, the biochemical properties of particular neuregulin isoforms, was characterized. These results suggest that neuregulins acting in injured peripheral nerve are part of a complex and tightly regulated network of autocrine/paracrine signals. The operation of this network may rely, in part, on the synthesis of structurally and functionally distinct neuregulin splice variants by specific cellular populations within these tissues.

In one embodiment of the current invention, a cDNA encoding SMDFβ1a, a novel sensory and motor neuron-derived factor (SMDF) splice variant isoform cDNA, is provided. The instant invention is also directed to an isolated. SMDFβ1a protein and a plasmid allowing expression of SMDFβ1a in a cell.

In another embodiment of the current invention, a cDNA encoding a second novel sensory and motor neuron-derived factor (SMDF) splice variant isoform, SMDFα2a, is described. The instant invention is directed to a plasmid containing this cDNA sequence and the regulatory elements necessary for expression of SMDFα2a in a cell and is also directed to an isolated SMDFα2a protein.

A further embodiment of the instant invention is a partial amino acid sequence of SMDF splice variant protein, SMDFα2b. The current invention includes an SMDFα2b protein containing this sequence as well as and a cDNA and plasmid encoding it.

Yet another embodiment of the instant invention comprises partial amino acid and nucleotide sequences of SMDF splice variant proteins SMDFβ2, SMDFβ3, and SMDFβ4. The instant invention is directed to isolated proteins containing these amino acid sequences as well as cDNA molecules and plasmids encoding them.

Yet another embodiment of the instant invention comprises partial amino acid and nucleotide sequences of glial growth factor splice variant proteins GGFβ1a, GGFβ2, GGFβ3, and GGFβ4. The instant invention is directed to isolated proteins containing these amino acid sequences as well as cDNA molecules and plasmids encoding them.

A further embodiment of the instant invention is a method of treating condition of nerve dysfunction comprising the step of administering an effective dose of SMDFβ1a, SGGFα2a, SMDFα2b, SMDFβ2, SMDFβ3, SMDFβ4, GGFβ1a, GGFβ2, GGFβ3, or GGFβ4. Such a method of treatment is likely to be useful in the treatment of demyelinating diseases such as multiple sclerosis, nerve injuries such as spinal cord and peripheral nerve injuries and neuropathies, neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, and motor neuron diseases such as ALS and Werdnig-Hoffman disease.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the matter in which the above-recited features, advantages and objects of the invention, as well as others which will become clear, are attained and can be understood in detail, more particular descriptions of the invention briefly summarized above may be had by reference to certain embodiments thereof which are illustrated in the appended drawings. These drawings form a part of the specification. It is to be noted, however, that the appended drawings illustrate preferred embodiments of the invention and therefore are not to be considered limiting in their scope.

FIGS. 1A-1D show nucleotide and deduced amino acid sequence of a rat SMDFβ1a cDNA clone isolated from a spinal cord/brainstem library. Numbering of the cDNA sequence is relative to the first nucleotide of the clone. The predicted amino acid sequence (underlined) corresponds to the largest open reading frame identified in the cDNA and is numbered (italicized, to right) relative to the first amino acid of this reading frame. Neuregulin protein domains are identified as follows: SMDF amino, the unique SMDF amino terminal domain; EGF-like Common, the portion of the neuregulin EGF-like domain common to all neuregulin isoforms; β, the neuregulin EGF-like β variant domain; 1, the “1” variant juxtamembrane domain; TM, transmembrane domain; Common Carboxy, intracellular domain common to all neuregulin transmembrane splice variants; “a” Variant Carboxy Terminus, the “a” variant carboxy terminal domain. Two hydrophobic segments representing potential membrane insertion signals are doubly underlined within the SMDF amino terminal domain. The protein coding sequences are preceded by a 635 bp 5′ untranslated region. This cDNA contains only 118 bp of 3′ untranslated region which does not include a polyadenylated tract.

FIG. 2 shows a comparison of the predicted full-length protein sequences of rat SMDFβ1a and human SMDFβ3 (Ho et al., 1995). Residues which differ between these sequences are indicated by asterisks. Dashes indicate gaps introduced to maximize alignment. The SMDF amino terminal domain sequences are boxed. Bold overlines designate the positions of two hydrophobic segments representing potential membrane insertion signals. The putative transmembrane segment is underlined in the rat SMDFβ1a sequence.

FIGS. 3A-3D shows nucleotide and deduced amino acid sequence of a rat SMDFα2a cDNA isolated from a JS1 schwannoma cDNA library. The predicted amino acid sequence (underlined) is derived from the largest open reading frame identified in this cDNA and is numbered (italicized, to right) relative to the first amino acid of this reading frame. Neuregulin protein domains are identified as follows: SMDF amino, the SMDF amino terminal domain; EGF-like Common, the portion of the EGF-like domain common to all neuregulin splice variants; α, the neuregulin EGF-like α domain; 2, the “2” variant juxtamembrane domain; TM, transmembrane domain; Common Carboxy, intracellular domain common to all neuregulin transmembrane precursors; “a” Variant Carboxy Terminus, the “a” variant carboxy terminal domain found in a subset of neuregulin transmembrane precursors. Two hydrophobic segments within the SMDF amino terminal domain which are potential membrane insertion signals are doubly underlined. A consensus polyadenylation signal within the 3′ untranslated region is boldly underlined.

FIGS. 4A-4C show rat SMDF cDNA sequences isolated from rat spinal cord/brainstem and JS1 schwannoma cDNA libraries and by reverse transcription-polymerase chain reaction using a rat lumbar dorsal root ganglion/spinal cord cDNA template. In FIG. 4A, boxes represent protein coding, 5′ and 3′ untranslated regions; connecting lines are included only to designate association of adjacent regions. Domains are indicated as follows: 5′ UTR, 5′ untranslated region; Amino, SMDF amino terminal domain with the internal dark bar marking the location of the putative membrane insertion signal within the SMDF amino terminal domain; EGF, the neuregulin EGF-like common domain; α and β, the neuregulin α and β EGF-like variant domains; 1,2,3 or 4, juxtamembrane domains; TM, transmembrane domain; Cytoplasmic, the intracellular domain common to all neuregulin transmembrane splice variants; a or b, variant carboxy terminal domains; 3′ UTR, 3′ untranslated region. The size of each isolated cDNA (in base pairs, bp) and the number of amino acid residues (aa) encoded by the corresponding cDNA is indicated to the right of each structure. Note that several of these cDNAs include only partial protein coding sequences and that the predicted protein sizes therefore do not reflect the complete length of the precursor protein. FIGS. 4B-4C show alignment of the deduced amino acid sequences of rat SMDFβ1a, SMDFβ2, SMDFβ3, SMDFβ4, SMDFα2a and SMDFα2b. The putative transmembrane segment is underlined. Dashes represent gaps introduced to produce optimal alignment of the sequences. The region demonstrating the greatest degree of sequence diversity, the EGF-like variable and juxtamembrane domains, is boxed. Arrowheads indicate positions of specific amino acids in the SMDF amino and EGF-like common domains differing between some clones. A bold bracket indicates the partial “b” variant carboxy terminus identified in one cDNA.

FIGS. 5A and 5B show Northern blot and PCR fingerprint analyses of SMDF splice variant expression in adult rat sciatic nerve and tissues containing the neurons contributing motor and sensory axons to this structure. FIG. 5A shows polyadenylated RNA (2 μg per lane) isolated from adult rat brain and spinal cord as well as from noninjured sciatic nerve (Noninj.) and sciatic nerve distal to a site of surgical transection 3 days postaxotomy (3 day) was blotted and probed for expression of SMDF transcripts. The probe, indicated in the diagram beneath the blot, is a 1014 bp fragment encoding sequences spanning the 5′ untranslated region and amino terminal half of the SMDF amino terminal region from pSLC135, the SMDFβ1a cDNA presented in FIG. 1. This probe detects two major mRNA transcripts, estimated at 3.5 and 7.5 kb (arrows, to left of diagram), in brain and spinal cord but not in noninjured or axotomized sciatic nerve. FIG. 5B shows PCR fingerprint analysis and indicates that neuregulin transmembrane isoforms, including SMDF splice variants, in rat lumbar dorsal root ganglia (DRG) and lumbar spinal cord (Spinal Cord) are overwhelmingly represented by β-isoforms. PCR was performed using cDNAs reverse transcribed from the indicated tissues and primers (arrows) hybridizing to sequences flanking the EGF-like domain and the juxtamembrane domains; these two regions are common to all known transmembrane neuregulin isoforms. PCR reactions were divided into thirds, with one portion digested with HaeIII (specifically cleaving PCR products encoding βneuregulin isoforms), the second portion digested with DdeI (specific for αneuregulin isoform cDNAs) and the third portion remaining undigested. Virtually all of the PCR product from DRG and spinal cord is cleaved by HaeIII to release a fragment of the expected 167 bp size. In contrast, DdeI produces no recognizable shift in the size of the PCR product. Consequently, neuregulins in the spinal cord and DRG, including SMDF isoforms, are predominantly represented by β-isoforms, with α-isoforms being undetectable in this assay.

FIGS. 6A and 6B show ribonuclease protection analyses of SMDF splice variant expression in adult rat nervous system. FIG. 6A shows that 10, 25 or 50 μg of total cellular RNA from adult rat brain, 50 μg of total cellular RNA from the rat JS1 schwannoma cell line or 50 μg of yeast tRNA was hybridized to an antisense ³²P-labeled riboprobe spanning the carboxy terminal portion of the SMDF amino terminus (SMDF), the neuregulin βEGF-like domain (EGF, β), the “1” juxtamembrane domain (1) and the initial portion of the transmembrane domain (TM; see diagram beneath autoradiogram). The diagram below the autoradiogram also indicates the fragment sizes expected for SMDFβ1, other SMDFβ isoforms (SDMFβ), SMDFα isoforms, neuregulinβ1 and neuregulinβ splice variants other than SMDF (EGFβ1 and EGFβ, respectively) and neuregulinα splice variants other than SMDFα (EGFα). Arrows to the light of the diagram indicate the positions of neuregulin splice variants detected following ribonuclease digestion; the size of standards, in base pairs, is indicated to the left of the diagram. FIG. 6B shows that 25 μg of total cellular RNA from adult rat whole brain (Brain), Cortex, Midbrain, Brainstem, Cerebellum, spinal cord (Cord), noninjured sciatic nerve (Noninj.Nerve), sciatic nerve distal to a site of surgical transection collected 7 days postaxotomy (7 DayNerve), adrenal gland (Adrenal) and lumbar dorsal root ganglia (DRG) was hybridized to the same SMDFβ1 riboprobe illustrated in A. Arrows to the right of the panel indicate the positions of neuregulin isoforms detected in this experiment. The sizes of standards, in base pairs (bp) is indicated on the left of the panel.

FIGS. 7A and 7B shows distribution of SMDF expression in adult rat tissues analyzed by Northern blot and reverse transcription-polymerase chain reaction analyses. FIG. 7A shows that 10 μg of total cellular RNA isolated from gastrocnemius/soleus muscle (Muscle), skin from the dorsum of the hindfoot (Skin), Testis, Kidney, small intestine (Sm. Intestine), Stomach, Liver, Spleen, Thymus, Lung and Heart was resolved by electrophoresis, blotted and probed with the 1014 bp SMDF-specific probe illustrated in FIG. 5. In this prolonged (two week) exposure, bands of estimated at 2.5, 3.5 and 7.5 kb sizes are detected in total cellular RNA from several non-neural tissues, including stomach and testis. FIG. 7B shows that templates for reverse transcription were prepared from 5 μg of total cellular RNA isolated from the indicated tissues. PCR was performed using these templates or a water blank (Blank) with primers hybridizing to sequences in the SMDF amino terminus and the transmembrane domain (Arrows); the sequences recognized by these primers are common to all SMDF transmembrane isoforms. Tissues examined include whole adult rat brain (Brain), Cortex, Cerebellum, Brainstem, Spinal Cord, Adrenal, sciatic nerve [both Noninjured and distal to a site of surgical transection 3 days after axotomy (3 days distal)], Heart, Lung, Thymus, Spleen, Liver, Stomach, large intestine (Large Int.), Kidney, Testis, skin from the dorsum of the hind foot (Skin) and gastrocnemius/soleus muscle (Muscle). In these experiments, SMDF transcripts were routinely detected in virtually all tissues in the body except spleen; in some experiments, SMDF mRNA was also detectable in this tissue.

FIG. 8 shows Chinese hamster ovary (CHO) cells expressing SMDF isoforms secrete functional neuregulin into their media. Monolayers of MCF-7 breast carcinoma cells were serum-starved and then challenged for 15 minutes with serum-free medium alone, serum-free media with 0.1% bovine serum albumin (BSA), 10 nM bacterially produced neuregulinβ1₁₆₈₋₂₃₇ or conditioned medium from four CHO cell lines stably transfected with a plasmid directing the expression of SMDFβ1a. Cell lysates were prepared from these lysates, immunoblotted and probed with a rabbit polyclonal antiphosphotyrosine antibody. A 185 kD band was detected in lysates of cells stimulated with neuregulinβ1₁₆₈₋₂₃₇ or media conditioned by each of the four SMDFβ1a expressing cell lines, but not from cells challenged with serum-free medium alone or containing 0.1% BSA.

FIGS. 9A-9E show the nucleotide and deduced amino acid sequence of a rat GGFβ1a cDNA clone and genomic sequences encoding the amino terminus of this cDNA. FIGS. 9A-9D: numbering of this rat GGFβ1a cDNA sequence is relative to the first nucleotide of the clone. The predicted amino acid sequence (underlined) corresponds to the largest open reading frame identified in the cDNA and is numbered (italicized, to right) relative to the first amino acid of this reading frame. Neuregulin protein domains are identified as follows: Kringle, the GGF amino terminal domain; Ig-Like, the neuregulin immunoglobulin-like domain; Glycosylation, a 34 amino acid region containing multiple potential sites of O- and N-linked glycosylation; EGF-like Common, the neuregulin EGF-like common domain; β, the neuregulin EGF-like β variant domain; 1, the “1” juxtamembrane domain; TM, transmembrane domain; Common Carboxy, intracellular domain common to all neuregulin transmembrane splice variants; “a” Variant Carboxy Terminus, the “a” variant carboxy terminal domain. A region which we have noted to be poorly conserved between the rat and human sequences is doubly underlined in the kringle domain. FIG. 9E: nucleotide and deduced amino acid sequence of genomic DNA encoding the rat GGF amino terminus. Numbering of the genomic sequence (nonitalicized, to right) is relative to the first nucleotide of the sequence presented above. The predicted amino acid sequence indicated partially overlaps with the amino terminus of the GGFβ1a protein presented in A (amino acid residues 74-244 of the protein sequence derived from this genomic clone; italicized numbers, to right). The methionine residue designated as the translation start site represents the first methionine present in this reading frame and is preceded by several termination codons.

FIGS. 10A-10B show the comparison of rat GGFβ1a and human GGF-II proteins. The predicted full-length protein sequences of rat GGFβ1a and human GGF-II [GGFβ3 {Marchionni, Goodearl, et al. 1993 ID: 77}(GenBank accession no. AAB59622)] were aligned by the Clustal method. Residues differing between these sequences are indicated by asterisks. Dashes indicate gaps introduced to maximize alignment. Neuregulin protein domains are identified as follows: Kringle, the GGF amino terminal domain; Ig-Like, the neuregulin immunoglobulin-like domain; Glycosylation, a 34 amino acid region containing multiple potential sites of O- and N-linked glycosylation; EGF-like Common, the neuregulin EGF-like common domain; β, the neuregulin EGF-like β variant domain; JM, juxtamembrane domains; TM, transmembrane domain; Common Carboxy, intracellular domain common to all neuregulin transmembrane splice variants; “a” Variant Carboxy Terminus, the “a” variant carboxy terminal domain. Note that the human sequence lacks the glycosylation domain identified in the rat sequence. The rat and human sequences also have distinct juxtamembrane domains; human GGF-II has a “3” juxtamembrane domain which contains a termination codon, allowing its synthesis as a directly secreted protein. In contrast, the EGF-like domain of the rat protein is coupled to a “1” juxtamembrane domain which is followed by a transmembrane domain and extensive cytoplasmic sequences. In contrast to human GGF-II, the rat GGFβ1a protein is synthesized as a transmembrane precursor requiring proteolytic cleavage for release.

FIGS. 11A-11C show a comparison of the structure of GGF cDNAs isolated from postaxotomy sciatic nerve, DRG and cord and their encoded proteins. FIG. 11A: Rat GGF structures predicted from cDNA sequences isolated from a rat JS1 schwannoma cDNA library and by reverse transcription-polymerase chain reaction using a rat lumbar dorsal root ganglion/spinal cord cDNA template. Boxes represent protein coding, 5′ and 3′ untranslated regions; connecting lines are included only to indicate association of adjacent regions. Domains are indicated as follows: Kringle, the GGF amino terminal domain; Ig-Like, the neuregulin immunoglobulin-like domain; Glycosylation, a 34 amino acid region containing multiple potential sites of O- and N-linked glycosylation; EGF, the neuregulin EGF-like common domain; β, the neuregulin β EGF-like variant domain; 1,2,3 or 4, juxtamembrane domains; Cytoplasmic, the intracellular domain common to all neuregulin transmembrane splice variants; a or b, variant carboxy terminal domains; 3′UTR, 3′ untranslated region. The size of the isolated cDNA (in base pairs, bp) and the number of amino acid residues (aa) encoded by each of these clones is indicated to the right of each structure. Note that several of these cDNAs include only partial protein coding sequences and that the sizes therefore do not reflect the complete length of the precursor protein. (FIGS. 11B-11C) Alignment of the deduced amino acid sequences of rat GGFβ1a, GGFβ2, GGFβ3 and GGFβ4. Dashes represent gaps introduced to produce optimal alignment of the sequences. Arrowheads indicate positions of amino acid residues differing between some isolated clones. The region of maximum sequence diversity among these sequences is boxed.

FIG. 12 shows the distribution of GGF expression in adult rat tissues analyzed by Northern blot analysis. 10 μg of total cellular RNA isolated from the indicated tissues was resolved by electrophoresis, blotted and probed with a 432 bp GGF-specific probe encoding a portion of the kringle domain. In this exposure, predominant 2.5-3.0 kb bands are detected in total cellular RNA from both neural and non-neural tissues, albeit with differing levels of expression; longer exposures of these same blots also demonstrate the presence of lesser amounts of larger transcripts (data not shown). Tissues examined include whole adult rat brain (Brain), Cortex, Cerebellum, Midbrain, Brainstem, spinal cord (Sp. Cord), Adrenal, JS1 schwannoma cells (JS1), Heart, Lung, Thymus, Spleen, Liver, Stomach, small intestine (Sm.Intestine), Kidney, Testis, skin from the dorsum of the hind foot (Skin) and gastrocnemius/soleus muscle (Muscle).

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention there may be employed conventional molecular biology, microbiology, and recombinant DNA techniques within the skill of the art. Such techniques are explained fully in the literature. See, e.g., Maniatis, Fritsch & Sambrook, “Molecular Cloning: A Laboratory Manual (1982); “DNA Cloning: A Practical Approach,” Volumes I and II (D. N. Glover ed. 1985); “Oligonucleotide Synthesis” (M. J. Gait ed. 1984); “Nucleic Acid Hybridization” [B. D. Hames & S. J. Higgins eds. (1985)]; “Transcription and Translation” [B. D. Hames & S. J. Higgins eds. (1984)]; “Animal Cell Culture” [R. I. Freshney, ed. (1986)]; “Immobilized Cells And Enzymes” [IRL Press, (1986)]; B. Perbal, “A Practical Guide To Molecular Cloning” (1984). Therefore, if appearing herein, the following terms shall have the definitions set out below.

As used herein, the term “cDNA” shall refer to the DNA copy of the mRNA transcript of a gene.

As used herein, the term “derived amino acid sequence” shall mean the amino acid sequence determined by reading the triplet sequence of nucleotide bases in the cDNA.

As used herein the term “screening a library” shall refer to the process of using a labeled probe to check whether, under the appropriate conditions, there is a sequence complementary to the probe present in a particular DNA library. In addition, “screening a library” could be performed by PCR.

As used herein, the term “PCR” refers to the polymerase chain reaction that is the subject of U.S. Pat. Nos. 4,683,195 and 4,683,202 to Mullis, as well as other improvements now known in the art.

The amino acid described herein are preferred to be in the “L” isomeric form. However, residues in the “D” isomeric form can be substituted for any L-amino acid residue, as long as the desired functional property is retained by the polypeptide. NH₂ refers to the free amino group present at the amino terminus of a polypeptide. COOH refers to the free carboxy group present at the carboxy terminus of a polypeptide. In keeping with standard polypeptide nomenclature, J Biol. Chem., 243:3552-59 (1969), abbreviations for amino acid residues are known in the art.

It should be noted that all amino-acid residue sequences are represented herein by formulae whose left and right orientation is in the conventional direction of amino-terminus to carboxy-terminus. Furthermore, it should be noted that a dash at the beginning or end of an amino acid residue sequence indicates a peptide bond to a further sequence of one or more amino-acid residues.

A “replicon” is any genetic element (e.g., plasmid, chromosome, virus) that functions as an autonomous unit of DNA replication in vivo; i.e., capable of replication under its own control.

A “vector” is a replicon, such as plasmid, phage or cosmid, to which another DNA segment may be attached so as to bring about the replication of the attached segment.

A “DNA molecule” refers to the polymeric form of deoxyribonucleotides (adenine, guanine, thymine, or cytosine) in its either single stranded form, or a double-stranded helix. This term refers only to the primary and secondary structure of the molecule, and does not limit it to any particular tertiary forms. Thus, this term includes double-stranded DNA found, inter alia, in linear DNA molecules (e.g., restriction fragments), viruses, plasmids, and chromosomes. In discussing the structure herein according to the normal convention of giving only the sequence in the 5′ to 3′ direction along the nontranscribed strand of DNA (i.e., the strand having a sequence homologous to the mRNA).

An “origin of replication” refers to those DNA sequences that participate in DNA synthesis.

A DNA “coding sequence” is a double-stranded DNA sequence which is transcribed and translated into a polypeptide in vivo when placed under the control of appropriate regulatory sequences. The boundaries of the coding sequence are determined by a start codon at the 5′ (amino) terminus and a translation stop codon at the 3′ (carboxyl) terminus. A coding sequence can include, but is not limited to, prokaryotic sequences, cDNA from eukaryotic mRNA, genomic DNA sequences from eukaryotic (e.g., mammalian) DNA, and even synthetic DNA sequences. A polyadenylation signal and transcription termination sequence will usually be located 3′ to the coding sequence.

Transcriptional and translational control sequences are DNA regulatory sequences, such as promoters, enhancers, polyadenylation signals, terminators, and the like, that provide for the expression of a coding sequence in a host cell.

A “promoter sequence” is a DNA regulatory region capable of binding RNA polymerase in a cell and initiating transcription of a downstream (3′ direction) coding sequence. For purposes of defining the present invention, the promoter sequence is bounded at its 3′ terminus by the transcription initiation site and extends upstream (5′ direction) to include the minimum number of bases or elements necessary to initiate transcription at levels detectable above background. Within the promoter sequence will be found a transcription initiation site, as well as protein binding domains (consensus sequences) responsible for the binding of RNA polymerase. Eukaryotic promoters often, but not always, contain “TATA” boxes and “CAT” boxes. Prokaryotic promoters contain Shine-Dalgarno sequences in addition to the −10 and −35 consensus sequences.

An “expression control sequence” is a DNA sequence that controls and regulates the transcription and translation of another DNA sequence. A coding sequence is “under the control” of transcriptional and translational control sequences in a cell when RNA polymerase transcribes the coding sequence into mRNA, which is then translated into the protein encoded by the coding sequence.

A “signal sequence” can be included near the coding sequence. This sequence encodes a signal peptide, N-terminal to the polypeptide, that communicates to the host cell to direct the polypeptide to the cell surface or secrete the polypeptide into the media, and this signal peptide is clipped off by the host cell before the protein leaves the cell. Signal sequences can be found associated with a variety of proteins native to prokaryotes and eukaryotes.

The term “oligonucleotide”, as used herein in referring to the probe of the present invention, is defined as a molecule comprised of two or more ribonucleotides, preferably more than three. Its exact size will depend upon many factors which, in turn, depend upon the ultimate function and use of the oligonucleotide.

The term “primer” as used herein refers to an oligonucleotide, whether occurring naturally as in a purified restriction digest or produced synthetically, which is capable of acting as a point of initiation of synthesis when placed under conditions in which synthesis of a primer extension product, which is complementary to a nucleic acid strand, is induced, i.e., in the presence of nucleotides and an inducing agent such as a DNA polymerase and at a suitable temperature and pH. The primer may be either single-stranded or double-stranded and must be sufficiently long to prime the synthesis of the desired extension product in the presence of the inducing agent. The exact length of the primer will depend upon many factors, including temperature, source of primer and use the method. For example, for diagnostic applications, depending on the complexity of the target sequence, the oligonucleotide primer typically contains 15-25 or more nucleotides, although it may contain fewer nucleotides.

The primers herein are selected to be “substantially” complementary to different strands of a particular target DNA sequence. This means that the primers must be sufficiently complementary to hybridize with their respective strands. Therefore, the primer sequence need not reflect the exact sequence of the template. For example, a non-complementary nucleotide fragment may be attached to the 5′ end of the primer, with the remainder of the primer sequence being complementary to the strand. Alternatively, non-complementary bases or longer sequences can be interspersed into the primer, provided that the primer sequence has sufficient complementary with the sequence or hybridize therewith and thereby form the template for the synthesis of the extension product.

As used herein, the terms “restriction endonucleases” and “restriction enzymes” refer to enzymes, each of which cut double-stranded DNA at or near a specific nucleotide sequence.

A cell has been “transformed” by exogenous or heterologous DNA when such DNA has been introduced inside the cell. The transforming DNA may or may not be integrated (covalently linked) into the genome of the cell. In prokaryotes, yeast, and mammalian cells for example, the transforming DNA may be maintained on an episomal element such as a plasmid. With respect to eukaryotic cells, a stably transformed cell is one in which the transforming DNA has become integrated into a chromosome so that it is inherited by daughter cells through chromosome replication. This stability is demonstrated by the ability of the eukaryotic cell to establish cell lines or clones comprised of a population of daughter cells containing the transforming DNA. A “clone” is a population of cells derived from a single cell or ancestor by mitosis. A “cell line” is a clone of a primary cell that is capable of stable growth in vitro for many generations.

Two DNA sequences are “substantially homologous” when at least about 75% (preferably at least about 80%, and most preferably at least about 90% or 95%) of the nucleotides match over the defined length of the DNA sequences. Sequences that are substantially homologous can be identified by comparing the sequences using standard software available in sequence data banks, or in a Southern hybridization experiment under, for example, stringent conditions as defined for that particular system. Defining appropriate hybridization conditions is within the skill of the art. See, e.g., Maniatis et al., supra; DNA Cloning, Vols. I & II, supra; Nucleic Acid Hybridization, supra.

A “heterologous” region of the DNA construct is an identifiable segment of DNA within a larger DNA molecule that is not found in association with the larger molecule in nature. Thus, when the heterologous region encodes a mammalian gene, the gene will usually be flanked by DNA that does not flank the mammalian genomic DNA in the genome of the source organism. In another example, coding sequence is a construct where the coding sequence itself is not found in nature (e.g., a cDNA where the genomic coding sequence contains introns, or synthetic sequences having codons different than the native gene). Allelic variations or naturally-occurring mutational events do not give rise to a heterologous region of DNA as defined herein.

As used herein, the term “host” is meant to include not only prokaryotes but also eukaryotes such as yeast, plant and animal cells. A recombinant DNA molecule or gene which encodes a protein of the present invention can be used to transform a host using any of the techniques commonly known to those of ordinary skill in the art. Prokaryotic hosts may include E. coli, S. tymphimurium, Serratia marcescens and Bacillus subtilis. Eukaryotic hosts include yeasts such as Pichia pastoris, mammalian cells and insect cells.

In general, expression vectors containing promoter sequences which facilitate the efficient transcription of the inserted DNA fragment are used in connection with the host. The expression vector typically contains an origin of replication, promoter(s), terminator(s), as well as specific genes which are capable of providing phenotypic selection in transformed cells. The transformed hosts can be fermented and cultured according to means known in the art to achieve optimal cell growth.

Methods which are well known to those skilled in the art can be used to construct expression vectors containing appropriate transcriptional and translational control signals. See for example, the techniques described in Sambrook et al., 1989, Molecular Cloning: A Laboratory Manual (2nd Ed.), Cold Spring Harbor Press, N.Y. A gene and its transcription control sequences are defined as being “operably linked” if the transcription control sequences effectively control the transcription of the gene. Vectors of the invention include, but are not limited to, plasmid vectors and viral vectors.

Reverse transcription-polymerase chain reaction (RT-PCR) analyses suggest that axotomized sciatic nerve, DRG and spinal cord all contain complex mixtures of neuregulin isoforms, potentially representing a large number of previously undescribed splice variants with novel functional characteristics. Consequently, an exhaustive cloning approach was used to identify the neuregulin isoforms expressed in surgically transected rat sciatic nerve, postaxotomy lumbar dorsal root ganglia, postaxotomy lumbar spinal cord and JS1 schwannoma cells, a rat line mimicking at least some characteristics of primary cultures of neonatal rat Schwann cells. The structure of cDNAs encoding six SDMF splice variants and four GGF isoforms was determined, representing both directly secreted proteins and transmembrane precursors.

These proteins demonstrate extensive structural variability in multiple regions, suggesting they are functionally distinct. These results suggest that neuregulins acting in injured peripheral nerve are part of a complex and tightly regulated network of autocrine/paracrine signals. The operation of this network may rely, in part, on the synthesis of structurally and functionally distinct neuregulin splice variants by specific cellular populations within these tissues.

The current invention is directed to SMDFβ1a, a sensory and motor neuron-derived factor (SMDF) splice variant isoform. The instant invention also includes an isolated cDNA encoding SMDFβ1a and a plasmid allowing expression of SMDFβ1a in a cell.

The instant invention is also directed to a second sensory and motor neuron-derived factor (SMDF) splice variant isoform, SGGFα2a. The instant invention also includes the cDNA encoding SMDFα2a as well as a plasmid containing this cDNA sequence and the regulatory elements necessary for expression the protein in a cell.

Yet another embodiment of the instant invention comprises the partial amino acid sequence of SMDF splice variant protein, SMDFα2b. The current invention includes an isolated SMDFα2b protein and a cDNA and a plasmid encoding this protein.

The instant invention is also directed to novel SMDF splice variant isoforms SMDFβ2, SMDFβ3, and SMDFβ4. Partial amino acid sequences for each of these proteins are given. The instant invention include proteins containing these sequences and cDNAs and plasmids encoding these proteins.

The current invention is further directed to comprises partial amino acid and nucleotide sequences of glial growth factor splice variant proteins GGFβ1a, GGFβ2, GGFβ3, and GGFβ4. The instant invention is also directed to isolated proteins containing these amino acid sequences as well as cDNA molecules and plasmids encoding them.

In addition, the instant invention is directed to a method of treating various forms of nerve dysfunction comprising the step of administering an effective dose of SMDFβ1a, SGGFα2a, SGGFα2b, SMDFβ2, SMDFβ3, SMDFβ4, GGFβ1a, GGFβ2, GGFβ3, or GGFβ4 to a patient to induce nerve repair Such a method is likely to find use in the treatment of demyelinating diseases such as multiple sclerosis, nerve injuries such as spinal cord and peripheral nerve injuries and neuropathies, neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, and motor neuron diseases such as ALS and Werdnig-Hoffman disease.

The following examples are given for the purpose of illustrating various embodiments of the invention and are not meant to limit the present invention in any fashion.

EXAMPLE 1 Cell Culture

MCF-7 breast carcinoma cells were obtained from the American Type Culture Collection (Rockville, Md.). JS1 rat schwannoma cells and DG44 Chinese hamster ovary (CHO) cells were provided by Drs. Eugene Johnson (Dept. of Pharmacology and Molecular Biology, Washington University School of Medicine) and Jeffrey Milbrandt (Dept. of Pathology, Washington University School of Medicine), respectively. MCF-7 cells were grown in minimal essential medium (MEM) supplemented with 10% fetal calf serum (FCS), 200 μM L-glutamine, 10 μg/ml streptomycin and 10 IU/ml penicillin. JS1 cells were cultured in Dulbecco's modified Eagle medium (DMEM) with 10% FCS, 200 μM L-glutamine, 10 μg/ml streptomycin and 10 IU/ml penicillin. DG44 CHO cells were grown in Ham's F12 medium supplemented with 10% FCS, 200 μM L-glutamine, 10 μg/ml streptomycin and 10 IU/ml penicillin.

EXAMPLE 2

Primary Cultures of Rat Neonatal Schwann Cells

Primary cultures of rat neonatal Schwann cells were established from the sciatic nerve of postnatal day five rat pups by the technique of Brockes et al. (1979). Contaminating fibroblasts were removed by treating cultures for 72 hours with 10⁻⁵M cytosine arabinoside. Cultures were then expanded in DMEM containing 10% FCS, 0.2 nM rNRGβ1₁₆₈₋₂₃₇ (see below), 5 μM forskolin, 200 μM L-glutamine, 10 μg/ml streptomycin and 10 IU/ml penicillin. 98-99% of the surviving cells were Schwann cells as assessed by their immunoreactivity for S100β. Schwann cells in their second and third passages were used for the experiments described in this work.

EXAMPLE 3

Isolation and Sequencing of Rat SMDF and GGF Precursor cDNA's Expressed in Spinal Cord

The isolation of four neuregulin cDNAs from a rat spinal cord/brainstem library was previously described (Carroll et al., 1997). Preliminary analysis revealed that clone pSLC135 was a SMDF splice variant while another clone, pSLC132, encoded a GGF splice variant. The complete nucleotide sequences of these cDNA's were determined using a commercial dye terminator cycle sequencing kit (Applied Biosystems, Inc.; Foster City, Calif.) with synthetic oligonucleotide primers and an automated sequencing machine (ABI Model 373A DNA Sequencing System). The resulting sequences were assembled and analyzed with the aid of Lasergene Seqman II software (Windows Version 3.58; DNAStar, Madison, Wis.).

EXAMPLE 4

Construction and Screening of a JS1 Schwannoma Cell cDNA Library

Polyadenylated RNA isolated from 80% confluent cultures of JS1 schwannoma cells was used to synthesize cDNA by the technique of Gubler and Hoffman (1983); cDNAs were synthesized in two separate reactions in which first strand synthesis was primed with either oligo dT or random hexamers. Following treatment with EcoRI methylase, T4 DNA polymerase and DNA polymerase I (Klenow fragment), double-stranded cDNA was ligated to EcoRI linkers and then digested with EcoRI. The resulting cDNA was fractionated by gel filtration chromatography and cDNAs larger than 500 bp were ligated to EcoRI digested λZAPII arms (Stratagene; La Jolla, Calif.). Ligated phage was packaged (Gigapack Gold; Stratagene) and plated on E. coli (XL-1 Blue mrf′ strain; Stratagene). A total of 2×10⁶ primary recombinants was amplified.

For screening, phage were plated at high density (50,000 plaques per plate), and duplicate filter lifts prepared from each plate (Maniatis et al., 1990). The insert from pSLC135 was ³²P-labeled by the random oligonucleotide priming method (Feinberg and Vogelstein, 1984) using a commercial kit (Prime-a-Gene Labeling System; Promega, Madison, Wis.) and labeled probe purified using spin columns (MidiSELECT-D columns; 5 Prime-3Prime, Inc., Boulder, Colo.). Radiolabeled probe (5×10⁵ cpm/ml) was hybridized to filters representing a total of 1.2×10⁶ plaque forming units under high stringency conditions [50% formamide/5×saline-sodium citrate (SSC)/5×Denhardt's'/0.1% sodium dodecyl sulfate (SDS) at 42° C.]. Filters were washed four times at room temperature in 2×SSC/0.1% SDS (fifteen minutes per wash) followed by two 68° C. washes in 0.2×SSC/0.1% SDS (one hour per wash). Three clones were identified in this manner and purified by limiting dilution (Maniatis et al., 1990). Plasmids were rescued from λ phage by coinfecting XL-1 Blue mrf′ bacteria with the λ phage and ExAssist helper phage (Stratagene) and then passaging the resulting rescued phagemid through E. coli (SOLR strain; Stratagene). Initial sequence analyses of two of the resulting cDNAs (pSLC275 and pSLC276) demonstrated them to be SMDF cDNAs. The complete sequence of these cDNAs was determined using an automated DNA sequencer and synthetic oligonucleotide primers as described above.

EXAMPLE 5

RACE Analyses

For rapid amplification of cDNA ends (RACE) analysis, the cDNA template was synthesized using a commercial kit (Marathon cDNA Amplification kit; CLONTECH Laboratories Inc., Palo Alto, Calif.) and polyadenylated RNA was isolated from JS1 schwannoma cells. 5′ RACE products were amplified from the JS1 cDNA by long-distance PCR (Expand High Fidelity kit; Boehringer-Mannheim) using the universal forward primer (AP1) supplied with the RACE kit and a reverse primer designed from either the sequence of the SMDFβ1a cDNA [pSLC135; primer sequence TATGTTCCTCCGCTGCCGGAA (SEQ ID No.: 14)] or the sequence of the GGFβ1a cDNA (pSLC132; primer sequence CAATCTGGGAGGCAGTGCGCA (SEQ ID No. 28). PCR parameters, after an initial two minute melt at 94° C., were thirty cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for two minutes, with a 20 second/cycle increase in the 72° C. step for cycles 11-30.

PCR products were resolved on a 1% gel, depurinated (10 minutes at room temperature in 0.25N HCl) and denatured (15 minute and 30 minute room temperature incubations in 0.5N NaOH/0.6M NaCl). Nucleic acids were then blotted to Sureblot membrane (Oncor; Gaithersburg, Md.) and baked per the manufacturer's recommendations. A 1014 bp BamHI/EcoRI fragment encoding the 5′ untranslated region and a portion of the amino terminus of a SMDFβ1a cDNA (pSLC135) was ³²P-labeled by the random oligonucleotide priming method (Feinberg and Vogelstein, 1984). Likewise, a 432 bp NotI fragment encoding a portion of the amino terminus (kringle domain) of a GGFβ1a cDNA (pSLC132) was ³²P-labeled by the same random priming method. Radiolabeled probes (5×10⁵ cpm/ml) were hybridized to the blots under high stringency conditions (50% formamide/5×SSC/5×Denhardt's/0.1% SDS at 42° C.). The blots were washed four times at room temperature in 2×SSC/0.1% SDS (15 minutes per wash), twice at 68° C. washes in 0.2×SSC/0.1% SDS (one hour per wash) and then exposed to Kodak XAR-5 film at −80° C. with two intensifying screens.

EXAMPLE 6

PCR Cloning of Additional SMDF and GGF Splice Variants

Oligonucleotides were designed with the aid of Lasergene PrimerSelect software (Windows Version 3.10; DNAStar) whenever possible. The common SMDF amino terminus forward oligonucleotides used for PCR of SMDF isoforms were designed from the sequence of a SMDFβ1a cDNA (clone pSLC135) and have the sequences GCTTTTCCTCCCTTTCAC (SEQ ID No.: 15) and CACCCACACAGAAGATGAGAG (SEQ ID No.: 16). The GGF amino terminus (kringle domain) forward primer used for amplification of GGF cDNAs was derived from the sequence of a GGFβ1a cDNA (pSLC132) and has the sequence ACCCTCTGCCTGCTGTCAACT (SEQ ID No.: 29). The common reverse oligonucleotide for PCR of SMDF and GGF transmembrane isoforms corresponds to nucleotides 1067-1049 of a rat NDF transmembrane precursor cDNA (GenBank accession no. U02323)(Wen et al., 1994). The specific α2 reverse oligonucleotide represents nucleotides 1058-1038 of a NDFα2b clone (GenBank accession no. U02316) (Wen et al., 1994). The specific β2 reverse primer corresponds to nucleotides 1049-1029 of a NDFβ2a cDNA (GenBank accession no. U02321) (Wen et al., 1994). The α-specific reverse oligonucleotide represents nucleotides 1040-1020 of a NDFα2b cDNA (GenBank accession no. U02316) (Wen et al., 1994). The β-specific reverse oligonucleotide spans residues 1034-1016 of a NDFβ2a clone (GenBank accession no. U02321) (Wen et al., 1994). The specific “4” juxtamembrane domain reverse oligonucleotide corresponds to nucleotides 1124-1101 of a NDFβ4a splice variant (GenBank accession no. U02322)(Wen et al., 1994). The specific reverse oligonucleotide for secreted SMDF and GGF isoforms corresponds to nucleotides 731-710 in the 3′ untranslated region of a NDFβ3 splice variant (GenBank accession no. U02315)(Wen et al., 1994).

Single-stranded cDNA templates were synthesized from polyadenylated RNA isolated from a pool of lumbar dorsal root ganglia and lumbar spinal cord (collected 7d and 10d postaxotomy) and a pool of sciatic nerve distal to a site of surgical transection (16 hr, 3d and 7d postaxotomy). Synthesis of cDNA was performed in a 20 μl reaction using random hexamer primers and Moloney murine leukemia virus reverse transcriptase (Superscript Plus; Life Technologies, Gaithersburg, Md.). After completion of reactions, samples were diluted to 100 μl with distilled water, boiled for five minutes and stored at −20° C. until use. Two microliters of cDNA was used as PCR template in reactions performed for 35 cycles of 94° C. for 1 min., 55° C. for 1 min. and 72° C. for 2 min. After verification of synthesis by gel electrophoresis, PCR products were chloroform extracted, ligated directly into the EcoRV site of pT7Blue or pT7Blue-3, and ligations were transformed into E. coli (NovaBlue strain) as recommended by the manufacturer (Novagen). The identity and sequence of the clones was then determined by cycle sequencing using an automated sequencer (see above).

A partial SMDF and GGF cDNA's were amplified using long-distance (LD)-PCR performed as per the manufacturer's recommendations (Expand High Fidelity kit; Boehringer-Mannheim), with a rat spinal cord/DRG cDNA template produced. Conditions used for this LD-PCR were identical to the conditions described above (see RACE Analyses). The resulting PCR product was cloned into pT7Blue-3 and sequenced as described above.

EXAMPLE 7

Northern Blot Analyses

Total cellular RNA was isolated from tissues by the technique of Chomczynski and Sacchi (1987). Polyadenylated RNA was isolated from total cellular RNA by oligo dT affinity chromatography (Oligotex Kit; Qiagen). For. Northern blot analyses, fifteen micrograms of each total cellular RNA or one microgram of each polyadenylated RNA was fractionated on 1% agarose gels containing 2.2M formaldehyde and transferred to Sureblot nylon membrane (Oncor; Gaithersburg, Md.) per the manufacturer's recommendations. Blots were baked under vacuum for 30 minutes at 80° C. Following a 1-2 hour prehybridization at 42° C. in Hybrisol III (45% formamide/5×SSC/10% dextran sulfate/1% SDS/100 μg/ml denatured salmon sperm DNA/1 μg/ml poly A), membranes were hybridized for 16-24 hours with DNA probes (5×10⁵ cpm/ml) 32P-labeled by the random oligonucleotide priming method (Feinberg and Vogelstein, 1984). Blots were washed three times in 2×SSC/0.5% SDS at room temperature (15 minutes per wash) followed by two washes (30 minutes per wash) in 0.2×SSC/0.5% SDS at 68° C. Membranes were exposed to Kodak XAR-5 film at −80° C. with two intensifying screens.

EXAMPLE 8

Ribonuclease Protection Assays

The template used to produce a ³²P-labeled riboprobe for ribonuclease protection assays was pSLC331 (encoding a portion of the SMDF amino terminus, EGF-like β1 domain and a small region of the transmembrane domain). ³²P-labeled riboprobes were transcribed from the linearized template with T7 RNA polymerase and purified from 5% polyacrylamide gels containing 8M urea. After initial optimization of hybridization conditions and RNase concentrations, ribonuclease protection assays were performed with an RPA II kit following the manufacturer's recommendations (Ambion; Austin, Tex.). Protected fragments were resolved on 5% polyacrylamide gels containing 8M urea. Gels were dried and exposed to Kodak XAR-5 film at −80° C. with two intensifying screens to visualize reaction products. Size standards used in these experiments were pBluescript II KS(+) digested with HpaII and ³²P-end-labeled with DNA polymerase I (Kienow fragment). In some experiments, a cyclophilin riboprobe transcribed from pSLC109 (Carroll and Frohnert, 1998) was hybridized to RNA together with the SMDF riboprobes to verify recovery of protected fragments.

EXAMPLE 9

Reverse Transcription (RT)-PCR Detection and Fingerprint Analyses of SMDF Isoforms in Rat Tissues

Five micrograms of total cellular RNA isolated from tissues of interest was treated with 3U of RNase-free DNase (RQ1 DNase; Promega) for 1 hour at 37° C. in MMLV reverse transcription buffer and then heated for five minutes at 95° C. RNA was then reverse transcribed in a 20 μl reaction with random hexamer primers and MMLV reverse transcriptase; a portion of each DNase digested sample was not reverse transcribed and was used to verify an absence of genomic DNA contamination. After completion of the reactions, samples were diluted to 100 μl with distilled water, boiled for five minutes and stored at −20° C. until use.

For detection of SMDF RNA, two non-overlapping pairs of primers were used in independent experiments. The first set of primers used was the first common SMDF amino terminus primer and the common reverse primer for transmembrane isoforms described above. The second set of primers corresponds to sequences in the 5′ untranslated region of a SMDFβ1a cDNA (pSLC135) and have the sequences CAGACGCCTGAGGTGAGAAACAT (SEQ ID No.: 17) and AAGTCCAAGGCAATTACCCAAAGT (SEQ ID No.: 18). 0.6 μM concentrations of each primer were used in reactions containing 5 μl of cDNA template; 1×Taq buffer; 1.5 mM MgCl₂; 80 μM each of dATP, dGTP and dTTP; 40 μM dCTP; 1.5 μCi of α-³²P-dCTP and 1.5 U Taq polymerase in a 50 μl reaction volume. Cycle parameters, following an initial two minute melt at 94° C., were 35 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 2 minutes. Ten microliters of each PCR reaction was resolved on 5% polyacrylamide gels containing 0.5×TBE (44.5 mM Tris/44.5 mM boric acid/1 mM EDTA). Gels were dried and reaction products visualized by exposing gels to Kodak XAR-5 film at −80° C. with two intensifying screens.

For PCR fingerprint analyses, PCR reactions were performed with α-³²P-dCTP as described above. After completion of the PCR reaction, 20 μl aliquots were digested with restriction endonucleases in a 50 μl reaction volume. The entire restriction digestion as well as the remaining 10 μl of undigested PCR product was resolved on 5% polyacrylamide gels containing 0.5×TBE. Gels were dried and exposed to Kodak XAR-5 film at −80° C. with two intensifying screens.

EXAMPLE 10

In situ Hybridizations

Surgical transection of one sciatic nerve was performed on adult (300-350 g male Harlan Sprague-Dawley rats as previously described (Carroll et al., 1997; Carroll and Frohnert, 1998). At the desired postaxotomy interval, rats were anesthetized and perfused transcardially first with 0.85% saline and then with 4% paraformaldehyde in phosphate-buffered saline (PBS; pH 7.4). Lumbar DRG and the lumbar enlargement of the spinal cord were dissected free and postfixed overnight at 4° C. in 4% paraformaldehyde in PBS. The next morning, tissues were rinsed twice with ice-cold PBS, transferred to 0.5M sucrose in PBS and equilibrated at 4° C. for 24-38 hrs. In situ hybridizations were performed using eight micron cryosections as previously described (Carroll et al., 1992). Sense and antisense ³³P-labeled riboprobes were transcribed from plasmids pSLC123 (encoding NRG EGF-like common, EGF-like β and 1 juxtamembrane domains) and pSLC111 (encoding the NRG immunoglobulin-like domain).

EXAMPLE 11

Production of Bacterially-Expressed Truncated Neuregulin

Truncated rat NRGβ1 containing the EGF-like and juxtamembrane regions (rNRGβ1₁₆₈₋₂₃₇) was produced using the bacterial expression vector pSLC219, which contains the indicated amino acids under the control of the T7lac promoter in pET28b(+) (Novagen); this vector was selected for the production of recombinant neuregulin after preliminary experiments with other expression vectors [pET21b(+), pET22b(+)] demonstrated that neither varying the size of the resulting protein or attempting to direct its secretion into the periplasmic space prevented bacteria from sequestering recombinant protein into inclusion bodies.

For expression of recombinant protein, pSLC219 was transferred into the BL21(DE3) strain of E. coli. 50 ml cultures were grown to an OD₆₀₀ of 0.6 and expression induced with 1 mM isopropyl-1-thio-β-D-galactopyranoside (IPTG) for three hours. Bacteria were pelleted and lysed by sonication in 1×binding buffer [20 mM Tris (pH 7.9)/0.5 M NaCl/5 mM imidazole] containing 6M guanidinium isothiocyanate. Recombinant protein was bound to nickel chelate columns (His-Bind resin; Novagen). Bound recombinant protein was washed with 1×wash buffer [20 mM Tris (pH 7.9)/0.5 M NaCl/60 mM imidazole] and then eluted with elution buffer [20 mM Tris (pH 7.9)/0.5 M NaCl/1M imidazole] containing 8M urea. Denatured neuregulin protein was refolded by sequential dialysis against a base buffer [10 mM Tris (pH 7.9)/100 mM NaH₂PO₄/150 mM NaCl/3 mM cysteine/10% glycerol/0.02% Tween-20] containing progressively decreasing concentrations of urea (8M, 4M, 2M, 1M, 0.5 M urea; 24 hours dialysis per step) and then against 1×phosphate buffered saline (PBS) containing 10% glycerol. Using this approach, 5-6 mg of recombinant protein is typically obtained from a 50 ml bacterial culture. The resulting protein is >98% pure as assessed by analytical reverse phase high pressure liquid chromatography. Protein preparations were assayed for bacterial endotoxin contamination using a Limulus amebocyte lysate assay (BioWhittaker; Walkerville, Md.) and verified to be free of detectable levels of endotoxin. Biological activity of the recombinant protein was assessed by examining its ability to stimulate erbB receptor tyrosine phosphorylation in MCF-7 cells (see below for specifics of this assay). With these preparations, maximal tyrosine phosphorylation is obtained with nanomolar concentrations of recombinant protein, a result identical to that previously reported with similarly truncated neuregulin proteins (Holmes et al., 1992; Peles et al., 1993).

EXAMPLE 12

Stable Expression of SMDF Protein in DG44 CHO Cells

To produce full-length recombinant SMDF protein in mammalian cells, the insert from pSLC135 (a SMDFβ1a cDNA) was excised with XhoI and NotI and cloned into the expression vector pBK-CMV (Stratagene) digested with the same enzymes to produce plasmid pSLC338.

EXAMPLE 13

Stable Expression of SMDF and GGF Proteins in DG44 CHO Cells

Nine micrograms of each SMDF or GGF expression plasmid, together with one microgram of a plasmid (pHLD-DHFR) expressing dihydrofolate reductase (DHFR) and carrying a genomic sequence promoting effective amplification of the transected sequences (the HSAG-1 element (McArthur and Stanners, 1991)), was transfected into a CHO line with a null mutation of the DHFR locus (DG44 CHO cells) by calcium precipitation (Chen and Okayama, 1987). Twenty-four hours after transfection, cells were refed with Ham's F12 supplemented with 10% FCS, 200 μM L-glutamine, 10 μg/ml streptomycin and 10 IU/ml penicillin. Seventy-two hours after transfection, cells were changed to MEMα medium (which selects for dhfr expression) containing 400 μg/ml G418 (which selects for the pBK-CMV resistance marker). After initial selection, expression of SMDF or GGF protein was amplified by selection with increasing concentrations of methotrexate. Pools of selected clones were used for subsequent experiments.

EXAMPLE 14

Assay of ErhB Tyrosine Phosphorylation in MCF-7 Cells

3×10⁵ MCF-7 breast carcinoma cells were plated in each well of a 24 well plate in MEM supplemented with 10% FCS, 10 μg/ml streptomycin and 10 IU/ml penicillin. Twenty-four hours after plating, the complete medium was replaced with MEM containing 0.1% bovine serum albumin (BSA) and the cells were serum-starved for two hours. Media was then replaced with MEM containing 0.1% BSA with specific concentrations of recombinant neuregulin or media conditioned by candidate cell lines. MCF-7 cells were stimulated for 15 minutes at 37° C. At the end of this time, media was removed and cells rinsed with Hanks' balanced salt solution. Cells were then lysed by the addition of 100 μl of 1×SDS sample buffer [0.125 M Tris (pH 6.6)/10% β-mercaptoethanol/2% SDS/2 μg/ml aprotinin/10 μg/ml leupeptin/2 mM PMSF/50 mM sodium fluoride/10 mM sodium orthovanadate/10 mM sodium molybdate/20 μM phenylarsine oxide/10 mM sodium pyrophosphate]. Lysates were collected and stored at −20° C. until use. 25 μl of each lysate was resolved on 8% SDS polyacrylamide gels and electroblotted onto PVDF membrane. Equivalent transfer was verified by Coomassie staining of residual protein in the gel. A rabbit polyclonal antiphosphotyrosine antibody (Transduction Laboratories; Lexington, Ky.) was diluted in TBST [0.15 M NaCl, 10 mM Tris (pH 8.0), 0.05% Tween 20, 0.002% sodium azide] containing 1% nonfat dry milk and applied to membranes. Horseradish peroxidase conjugated goat anti-rabbit secondary antibody (Jackson Immunoresearch Laboratories; West Grove, Pa.) was used at a 1:7000 dilution in TBST. Immunoreactive species were detected by enhanced chemiluminescence (Pierce).

EXAMPLE 15

Clone Designations and Nucleotide Sequence Accession Numbers

The SMDF clones isolated and their designations are as follows: SMDFβ1a, pSLC135; SMDFβ4, pSLC252; SMDFα2b, pSLC275; SMDFα2a, pSLC276; SMDFβ3, pSLC284; SMDFβ2, pSLC348. The GGF clones isolated and their designations are GGFβ1a, pSLC132; GGFβ2, pSLC346; GGFβ3, pSLC347; and, GGFβ4, pSLC345.

EXAMPLE 16

Nucleotide Sequence of a Rat SMDF Transmembrane Precursor Expressed in the Adult Central Nervous System

The isolation of four neuregulin cDNAs from a rat spinal cord/brainstem library was previously described (Carroll et al., 1997). Preliminary analyses indicated that one of these clones, plasmid pSLC135, encoded a previously undescribed SMDF transmembrane precursor protein. To fully establish the structure of this novel protein, the complete sequence of the pSLC135 cDNA was determined and is given in SEQ ID No. 1.

The largest open reading frame in this 2856 bp cDNA (FIGS. 1A-1D, underlined) begins with an ATG at nucleotide 636, extends to a TAA termination codon at residue 2736 and encodes a 700 amino acid polypeptide with predicted M_(r) 76,385. The amino acid sequence is listed in SEQ ID No. 2. These protein coding sequences are preceded by a 635 bp 5′ untranslated region. Rapid amplification of cDNA ends (RACE) performed using a rat JS1 schwannoma cell template (see below) followed by hybridization with SMDF specific probes internal to the expected amplified sequences identified no sequences extending beyond the 5′ end of the pSLC135 cDNA (data not shown), suggesting that this clone contains a nearly complete representation of the mRNA 5′ untranslated region. In contrast, the protein coding region of the pSLC135 cDNA is followed by only 118 bp of 3′ untranslated sequences which do not include a polyadenylated tract. Based on these structural characteristics and an estimate of a minimal 3.5 kb size for the major SMDF mRNAs expressed in spinal cord and brain (see below), it is likely that the pSLC135 cDNA does not include the entire length of 3′ untranslated region sequences present in the corresponding mRNA.

EXAMPLE 17

Deduced Amino Acid Sequence of the pSLC135 Rat SMDF

The amino terminal portion of the protein sequence predicted by the pSLC135 cDNA has several important structural features that confirm its identification as an SMDF isoform. A sequence database search with the protein sequence predicted by the pSLC135 cDNA established that the amino terminal region of this polypeptide (FIGS. 1A-1D, SMDF amino; FIG. 2, boxed sequences) is closely related (82.5% sequence identity) to the equivalent region of a protein encoded by a human SMDFβ3 cDNA(Ho et al., 1995) (Ho et al., 1995). As with ARIA (Falls et al., 1993), heregulin (Holmes et al., 1992), NDF (Wen et al., 1994) and human SMDF (Ho et al., 1995), the pSLC135 protein lacks a hydrophobic N-terminal signal peptide. Hydrophilicity analysis (Kyte and Doolittle, 1982) of the pSLC135 polypeptide instead demonstrates the presence of two hydrophobic regions near the N terminus, Ser⁴⁹-Leu⁶³ and Ile⁷⁷-Val¹⁰¹, which are highly conserved between rat and man [three conservative mutations in the first hydrophobic stretch and complete identity in the second (FIGS. 1A-1D, doubly underlined; FIG. 2, bars over the SMDF domain)]; it has been suggested that these hydrophobic stretches function as uncleaved internal signals for membrane translocation (Ho et al., 1995). Eight cysteine residues within the hydrophobic sequences are identically placed and conserved between these two species. Given the high degree of sequence conservation within the amino terminal domain and the identification of the conserved structural features noted above, it is concluded that the pSLC135 cDNA encodes a rat SMDF splice variant.

EXAMPLE 18

Relationship of Rat pSLC135 SMDF to Other SMDF Proteins

Although the protein encoded by the pSLC135 cDNA is clearly a member of the SDMF neuregulin subfamily, it is not the rat equivalent of the human SMDFβ3 isoform reported by Ho et al. (Ho et al., 1995). Alignment of the proteins predicted by the rat pSLC135 and human SMDFβ3 cDNAs shows that the closely related amino terminal sequences of these proteins (FIG. 2, boxed sequences) are both followed by an EGF-like domain containing a region common to all neuregulin isoforms and a β variant domain (one of two possible sequences, α or β, previously found in other neuregulins at this position). Thereafter the rat and human sequences diverge. The EGF-β variant domain of the human SMDFβ3 sequence is followed by an 11 amino acid region (a “3” juxtamembrane domain (Wen et al., 1994)) which culminates in a termination codon, thereby allowing the synthesis of this molecule in a directly secreted form.

In contrast, the EGF-β variant domain in the pSLC135 protein is followed by a nine amino acid juxtamembrane domain sequence (1, FIGS. 1A-1D) identical to a similarly located sequence in some NDF isoforms (Wen et al., 1994) which in turn is coupled to a large region identical to the equivalent portion of a protein sequence predicted by a NDFβ2a cDNA isolated from ras-transformed Rat-1-EJ cells (Wen et al., 1994). This large expanse of carboxy terminal sequence includes a 31 amino acid putative transmembrane domain (FIGS. 1A-1D, TM; FIG. 2, underlined), a 157 amino acid cytoplasmic region common to all neuregulin transmembrane precursors (FIG. 1, Common Carboxy), and a 219 amino acid “a” variant carboxy terminus [one of three alternative sequences (a, b or c) reported by Wen et al. (Wen et al., 1994) in rat NDF splice variants].

It is therefore apparent that, in contrast to the directly secreted human SMDFβ3 isoform, the rat pSLC135 protein is synthesized as a transmembrane precursor requiring proteolytic cleavage for the release of soluble factor. Following a convention which names neuregulin splice variants on the basis of their alternative usage of variable domains in the order amino terminus-EGF variable domain-juxtamembrane domain-variable carboxy terminal domain (Holmes et al., 1992; Wen et al., 1994), the protein encoded by the pSLC135 cDNA was designated as an SMDFβ1a isoform.

EXAMPLE 19

Analysis of SMDFα Isoforms Expressed by JSI Schwannoma Cells

In light of the extreme structural variability previously identified in the mesenchymal (heregulin/NDF) neuregulin subfamily (Wen et al., 1994), it is reasonable to postulate that the SMDF neuregulin subfamily may demonstrate a similar array of alternative forms with diverse functional characteristics. As an initial test of this hypothesis, an expanded search for SMDF cDNAs was undertaken. It was previously reported that the rat JS1 schwannoma cell line (Schubert et al., 1974) expresses a variety of neuregulin mRNAs, including transcripts encoding SMDF isoforms (Carroll et al., 1997). Therefore, a JS1 cDNA library was constructed and screened with the SMDFβ1a cDNA described above, resulting in the isolation of three additional neuregulin clones. Based on their characteristic amino terminal sequences, two cDNAs, 2.5 kb and 0.9 kb in length, were identified as SDMF isoforms; the third cDNA represents a novel GGF clone which will be described in Example 30.

EXAMPLE 20

Characterization of JS1 Schwannoma Cell pSLC276 SMDF cDNA

To establish the structure of the encoded proteins, the complete sequence of the two SMDF cDNAs isolated from JS1 schwannoma cells was determined. The larger of these cDNAs, pSLC276 (SEQ ID No. 4), spans 2540 bp, which includes a complete SMDF coding sequence, beginning with an ATG at nucleotide 370 and extending through a TAA termination codon at residue 2455 (FIGS. 3A-3D). This reading frame is preceded by 353 bp (nucleotides 18-369) of 5′ untranslated region which is completely colinear with the 5′ untranslated sequences present in the rat SMDFβ1a cDNA described above.

In contrast, the 3′ untranslated region of the pSLC276 cDNA differs from that of the pSLC135 clone. The coding sequences in the pSLC276 cDNA are followed by only a short region (63 bp) of 3′ untranslated sequences which show complete identity with the initial 63 bp of the 3′ untranslated region found in pSLC135. Notably, the truncated 3′ untranslated region of pSLC276 contains a consensus polyadenylation signal [AATAAA (SEQ ID No.: 19); nucleotides 2504-2508] which begins 18 bp 5′ of a 19 bp polyadenylated tract (FIGS. 3A-3D). Based on the identity of the initial sequences of the pSLC135 and pSLC276 3′ untranslated sequences, the presence of a polyadenylation consensus signal and a poly A(+) tract, it was concluded that the shortening of the 3′ untranslated region of the pSLC276 cDNA results from the utilization of alternative polyadenylation sites rather than an alternative splicing event involving the 3′ end of this transcript.

EXAMPLE 21

Protein Encoded by JS1 Schwannoma Cell pSLC276 SMDF cDNA

The protein sequence derived from the pSLC276 cDNA is also that of an SMDF transmembrane precursor protein. Translation of the largest open reading frame in this clone predicts a 695 amino acid polypeptide (M_(r) 75,646) (SEQ ID No. 5), which contains the distinctive SMDF amino terminus (FIGS. 3A-3D, SMDF amino). Alignment of the pSLC276 protein with the rat SMDFβ1a polypeptide (presented diagrammatically in FIG. 4A and as aligned sequences in FIGS. 4B-4C) demonstrates these sequences to be highly similar with the exception of the C terminal portion of the EGF-like domain and the adjacent segment coupling the EGF-like domain to the transmembrane segment and cytoplasmic domains. In the pSLC276 protein, the EGF-like β and “1” juxtamembrane domain are replaced by EGF-like α and “2” juxtamembrane domains (FIGS. 4B-4C, boxed). Following the nomenclature conventions cited above, the protein predicted by this cDNA is therefore an SMDFα2a isoform. Also of note are two conservative amino acid substitutions in the SMDF amino terminal sequences (FIGS. 4B-4C, first two arrowheads); it is currently unclear whether these changes represent simple polymorphisms, mutations arising in the neoplastic JS1 schwannoma cell line or cloning artifacts introduced during reverse transcription of the original mRNA.

EXAMPLE 22

JSI Schwannoma Cell pSLC275 SMDF cDNA

The second SMDF clone isolated from the JS1 schwannoma library, pSLC275, is a partial cDNA (SEQ ID No. 6) which encodes a portion of an SMDF transmembrane precursor protein (FIG. 4A). Alignment of the partial protein sequence (SEQ ID No. 7) predicted by the pSLC276 cDNA with the rat SMDFβ1a and SMDFα2a polypeptides shows that the pSLC275 protein is virtually identical to SMDFα2a with the exception of its last six amino acids (bracket, FIGS. 4B-4C). These sequences instead encode the first six amino acids of an alternative (“b” variant) carboxy terminal domain previously identified in a NDF transmembrane precursor (Wen et al., 1994). Accordingly, the protein encoded by the pSLC275 cDNA represents an SMDFα2b isoform.

EXAMPLE 23

Analysis of Additional SMDF Splice Variants Expressed in Rat Spinal Cord and Dorsal Root Ganglia Following Sciatic Axotomy

Although the cDNA library screens led to the identification of three novel rat SMDF splice variants (SMDFβ1a, SMDFα2a and SMDFα2b), considerably greater structural diversity is found in the rat NDF subfamily (seven isoforms (Wen et al., 1994)), suggesting that further SMDF splice variants remained unidentified. Therefore, reverse transcription-polymerase chain reaction (RT-PCR) was used to investigate the potential existence of additional SMDF isoforms expressed in the rat nervous system.

Dorsal root ganglion sensory and spinal cord motor neurons express high levels of SMDF mRNA (Ho et al., 1995), possibly representing a component of the “axon-associated mitogen” associated with newly extending axons of DRG sensory neurons (Morrissey et al., 1995). Accordingly, the cDNA template used for these experiments was prepared from a pool of total cytoplasmic RNA isolated from noninjured rat lumbar dorsal root ganglia and spinal cord and the same tissues collected 7 and 10 days after surgical transection of the sciatic nerve (a period during which neurite outgrowth is actively occurring).

The greatest degree of structural variability was observed clustered in the EGF-like variable and juxtamembrane domains. Multiple PCR primers were designed to amplify sequences encompassing the carboxy terminal portion of the SMDF amino terminus, the EGF-like common and variant domains, and the juxtamembrane domains of both directly secreted and transmembrane precursor SMDF isoforms. The reverse oligonucleotides used in these experiments included primers expected to hybridize to a target cDNA regardless of which EGF-like variant and juxtamembrane domains are present as well as oligonucleotides directed towards specific expected splice variants. All possible combinations of these primers were used to amplify SMDF sequences from the DRG/spinal cord template. After initial screening and grouping of 104 candidate cDNAs, representative clones from each group of PCR products were sequenced in their entirety. SMDF sequences were readily detectable in DRG and spinal cord with this analysis and were represented by multiple alternatively spliced transcripts. In addition to partial cDNAs with a sequence identical to that determined for pSLC135, the previously described SMDFβ1a clone, other clones were identified which had complete sequence identity with SMDFβ1a in the amino-terminal region and EGF-like domain, but diverged thereafter (FIG. 4A). In total, three additional SMDF cDNA were isolated which are SEQ ID No. 8 encoding SEQ ID No. 9, SEQ ID No. 10 encoding SEQ ID No. 11, and SEQ ID No. 12 encoding SEQ ID No. 13.

EXAMPLE 24

Comparison of Isolated SMDF Splice Variants to SMDFβ1a

A comparison of the complete sequences of each of the cDNAs isolated from JS1 cells, dorsal root ganglia, and spinal cord to that of the SMDFβ1a cDNA demonstrates that the larger cDNA isolated from the JS1 line contains a complete protein coding sequence whereas the other clones contain sequences encoding only a portion of each polypeptide (FIGS. 4A, B, C). These cDNAs include representatives of clones encoding six related SMDF precursor proteins. The amino terminal sequences and EGF-like common domain of the five additional predicted proteins are identical to that of SMDFβ1a, with no internal insertions or deletions seen in these structures in any clone. However, structural variation is present in three regions carboxy terminal to the constant regions.

First, the two cDNAs isolated from JSI cells contain an α EGFvariable domain rather than the β variable domain present in all clones isolated from spinal cord and DRG. Second, four distinct juxtamembrane domains were present which were identical to sequences previously designated as 1 to 4 in mesenchymal neuregulin isoforms (Wen et al., 1994). Lastly, two different variant carboxy terminal domains were identified in the clones isolated from JS1 schwannoma cells. A comparison of these latter sequences to those previously identified in the mesenchymal neuregulin subfamily demonstrates the variable carboxy terminal domains are identical to regions previously designated as “a” and “b” carboxy terminal sequences (Wen et al., 1994). Following the nomenclature convention noted above, the isolated SMDF cDNAs encode SMDFβ1a, SMDFα2a, SMDFα2b, SMDFβ2 (SEQ ID No. 8), SMDFβ3 (SEQ ID No. 10) and SMDFβ4 (SEQ ID No. 12) isoforms.

EXAMPLE 25

Northern Blot Analysis of SMDF mRNA Expression in Noninjured and Postaxotomy Rat Sciatic Nerve, Lumbar Spinal Cord and Dorsal Root Ganglia

To examine the specific expression and size of any SMDF transcripts in rat sciatic nerve and tissues containing the neurons projecting into this structure (lumbar spinal cord and the L4 to L6 dorsal root ganglia), Northern blot analyses were performed. Polyadenylated RNA isolated from adult rat brain (a control tissue expected to express SMDF mRNA), adult rat lumbar spinal cord, noninjured adult rat sciatic nerve and sciatic nerve collected 3 days after surgical transection was blotted and hybridized to a probe specific for SMDF mRNAs (spanning the 5′ untranslated region and a portion of the SMDF amino terminus; see the diagram at the bottom of FIG. 5A).

The results of a Northern blot analysis are shown in FIG. 5A. Two major SMDF messengers, 3.5 kb and 7.5 kb in size, are evident in poly A+ RNA from both adult rat brain and lumbar spinal cord, with the 3.5 kb mRNA being particularly prominent in spinal cord (FIG. 5A). In contrast, SMDF transcripts were undetectable in noninjured or 3 day postaxotomy sciatic nerve (FIG. 5A), even with prolonged (three week) exposures (data not shown). It is therefore apparent that sciatic nerve and spinal cord differ in their relative expression of this neuregulin subfamily.

EXAMPLE 26

Fingerprint Analyses of RT-PCR Products to Distinguish the Expression of the Splice Variants

Although it is evident from these experiments that SMDF mRNAs accumulate in adult rat lumbar spinal cord, little information is available regarding the structure of the SMDF splice variants present in this tissue. In particular, identification of SMDFα isoforms raises the question of whether these splice variants are also expressed by DRG sensory and spinal cord motor neurons, a finding which would have important biologic implications given the differing affinities and biologic activities of α and β neuregulins. As an initial assessment of a and β-isoform expression in lumbar spinal cord and dorsal root ganglia following nerve injury, fingerprint analyses of RT-PCR products were used to distinguish the expression of these splice variants.

For these experiments, the EGF-like domains of the neuregulin transmembrane precursors expressed in lumbar dorsal root ganglia and spinal cord (7 and 10 days after surgical transection of the sciatic nerve) were amplified using primers spanning this domain and the adjacent juxtamembrane domain. A portion of each product was then digested with restriction endonucleases specifically cleaving α or β isoforms. The results of this analysis are shown in FIG. 5B.

EXAMPLE 27

Ribonuclease Protection Analyses of SMDF Splice Variant Expression

SMDF splice variant expression in adult rat nervous system was analyzed by ribonuclease protection analysis. Total cellular RNA from adult rat brain or from rat JS1 schwannoma cell was hybridized to an antisense ³²P-labeled riboprobe spanning a region from the carboxy terminal portion of the SMDF amino terminus to the initial portion of the transmembrane domain. After hybridization and RNase digestion, protected fragments were resolved on 8M urea 5% polyacrylamide gels and exposed to autoradiography. The results of the RNAse protection are shown in FIG. 6A. The diagram below the autoradiogram indicates the fragment sizes expected for SMDFβ1, other SMDFβ isoforms (SDMFβ), SMDFα isoforms, NRGβ1, NRGβ splice variants EGFβ1 and EGFβ, and NRGα splice variants EGFα.

The same probe was used to perform RNAse protection analysis with total cellular RNA from adult rat whole brain, Cortex, Midbrain, Brainstem, Cerebellum, spinal cord, noninjured sciatic nerve, sciatic nerve distal to a site of surgical transection collected 7 days postaxotomy, adrenal gland, and lumbar dorsal root ganglia. These results are shown in FIG. 6B.

EXAMPLE 28

SMDF Expression Non-neural Adult Rat Tissues

SMDF expression was analyzed in adult rat tissues by Northern blot and reverse transcription-polymerase chain reaction analyses to determine if any SMDF isoforms were expressed in non-neural tissue. Tissues analyzed included gastrocnemius/soleus muscle, skin from the dorsum of the hindfoot, Testis, Kidney, small intestine, Stomach, Liver, Spleen, Thymus, Lung and Heart. The results of Northern blot analysis with the 1014 bp SMDF-specific probe (FIG. 5) are shown in FIG. 7A. In this prolonged (two week) exposure, bands of estimated at 2.5, 3.5 and 7.5 kb sizes are detected in total cellular RNA from several non-neural tissues, including stomach and testis.

For the reverse transcription-polymerase chain reaction analyses, total cellular RNA from whole adult rat brain, cortex, cerebellum, brainstem, spinal cord, adrenal, sciatic nerve [both Noninjured and distal to a site of surgical transection 3 days after axotomy (3 days distal)], heart, lung, thymus, spleen, liver, stomach, large intestine, kidney, testis, skin from the dorsum of the hind foot, and gastrocnemius/soleus muscle was reverse transcribed and PCR amplified with primers hybridizing to sequences in the SMDF amino terminus and the transmembrane domains. The sequences recognized by these primers are common to all SMDF transmembrane isoforms. The results are shown in FIG. 7B. In these experiments, SMDF transcripts were routinely detected in virtually all tissues in the body except spleen; in some experiments, SMDF mRNA was also detectable in this tissue.

EXAMPLE 29

Secretion of Functional SMDF Isoforms into the Media of Chinese Hampster Ovary (CHO) Cells

Transfection of plasmid pSLC338 into CHO cells resulted in four CHO cell lines expressing SMDFβ1a. To determine if the SMDFβ1a protein produced by these cell lines was functional, monolayers of MCF-7 breast carcinoma cells were serum-starved and then challenged for 15 minutes with serum-free medium alone, serum-free media with 0.1% bovine serum albumin (BSA), 10 nM bacterially produced neuregulinβ1₁₆₈₋₂₃₇ or conditioned medium from the four CHO cell expressing SMDFβ1a. Following this, cell lysates were prepared from the MCF-7 cells, immunoblotted and probed with a rabbit polyclonal antiphosphotyrosine antibody. The results are shown in FIG. 8. A 185 kD band was detected in lysates of cells stimulated with neuregulinβ1₁₆₈₋₂₃₇ or media conditioned by each of the four SMDFβ1a expressing CHO cell lines, but not from cells challenged with serum-free medium alone or media containing 0.1% BSA.

EXAMPLE 30

Sequencing and Characterization of GGFβ1a cDNA (Clone pSLC132)

Initial analyses indicated that the fourth NRG cDNA, clone pSLC132, previously identified in a rat spinal cord library (Carroll et al., 1997) encoded a previously undescribed transmembrane NRG isoform from the GGF subfamily. To establish the structure of the NRG isoform encoded by this clone, the complete sequence of the pSLC132 cDNA was determined.

The largest open reading frame in this 3086 bp cDNA (SEQ ID No.: 20) begins immediately at the 5′ end of the sequence and extends to a TAA termination codon at nucleotide 2361 (FIGS. 9A-9D). A comparison between the protein sequence predicted by the pSLC132 cDNA (SEQ ID No.: 21) and sequences currently deposited in GenBank showed a strong similarity to the sequence of human GGFβ3 (Marchionni et al., 1993). The amino terminal sequences of the rat cDNA are highly similar to the carboxy terminal half of the human GGF kringle domain with the exception of an amino acid region in the middle of this region. The predicted protein sequences C-terminal to this kringle domain are identical to those predicted by a rat NDFβ1a cDNA (Wen et al., 1994) and consist (in order) of an immunoglobulin-like domain, a glycosylation “spacer”, EGF-like common and b sequences, a hydrophobic transmembrane segment, a cytoplasmic domain common to all NRG transmembrane precursors and an “a” variant carboxy terminus. These potential protein coding sequences are followed by a 722 bp 3′ untranslated region which lacks a polyadenylated tract, suggesting that the pSLC132 cDNA does not completely represent the native 3′ untranslated region of the corresponding mRNA.

As the amino terminal sequences of the pSLC132 cDNA were apparently incomplete, the inserts from the pSLC132 clone and a near-full length SMDF transmembrane precursor cDNA (see below) were used to screen a rat genomic library, resulting in the isolation of twenty clones hybridizing to these probes. Three of these clones (λRNR24, 25 and 26) specifically hybridized to a probe derived from the kringle domain sequences of pSLC132. A 4.0 kb EcoRI fragment from λRNR26 Containing these hybridizing sequences was subcloned and sequenced. The protein coding sequences of the rat GGF kringle domain are contained within a single exon (FIG. 11A).

EXAMPLE 31

Structural Variability of GGF Splice Variants

Single-stranded cDNA templates were synthesized from polyadenylated RNA isolated from a pool of lumbar dorsal root ganglia and lumbar spinal cord (collected 7 and 10d postaxotomy) and a pool of sciatic nerve distal to a site of surgical transection (16 hr, 3d and 7d postaxotomy). Partial GGF cDNAs were produced using long-distance (LD)-PCR. Although the secreted isoforms (eg. GGFβ3) were generated with a single set of primers, cDNAs encoding GGF transmembrane isoforms (GGFβ2 and GGFβ4) were isolated using nested primer sets using the kringle domain forward oligonucleotide and the common transmembrane domain oligonucleotide. PCR products were cloned into pT7Blue-3 and sequenced as described above. A total of three novel partial cDNA sequences were generated: GGFβ2—SEQ ID No.: 22, GGFβ3—SEQ ID No.: 24, and GGF4—SEQ ID No.: 26). The predicted amino acid sequence are given in SEQ ID No. 23 (GGFβ2), SEQ ID No. 25 (GGFβ3), and SEQ ID No. 26 (GGFβ4).

Comparisons of these partial GGF sequences to the GGFβ1a are shown in FIGS. 11A-11C. i.e., shows a comparison of the structure of GGF cDNAs isolated from postaxotomy sciatic nerve, DRG and cord and their encoded proteins. FIG. 11A shows rat GGF structures as predicted from cDNA sequences including the neuregulin EGF-like common domain, the neuregulin β EGF-like variant domain, juxtamembrane domains, the intracellular domain common to all neuregulin transmembrane splice variants, and variant carboxy terminal domains. FIGS. 11B-11C show the alignments of the deduced amino acid sequences of rat GGFβ1a, GGFβ2, GGFβ3 and GGFβ4.

EXAMPLE 32

Analysis of GGF Expression in Adult Rat Tissues

FIG. 12 shows a detailed distribution of GGF expression in adult rat tissues analyzed by Northern blot analysis. The GGF expression in adult rat tissues was carefully analyzed by Northern blot, ribonuclease protection, and reverse transcription-polymerase chain reaction analyses. For Northern blot analysis, total cellular RNA isolated from various tissues and JS1 schwannoma cells was resolved by electrophoresis, blotted, and probed with the 1014 bp probe. The probe detects RNA of the expected size in the JS1 schwannoma control. In this long (two week) exposure, bands of differing sizes are also detected in total cellular RNA from non-neural tissues, including stomach and testis.

For the ribonuclease protection experiment, total cellular RNA isolated from the various tissues and JS1 schwannoma cells is hybridized to the antisense riboprobe.

Reverse transcription-polymerase chain reaction analyses was performed by amplifying total cellular RNA from whole adult rat brain, cortex, cerebellum, brainstem, spinal cord, adrenal, sciatic nerve [both Noninjured and distal to a site of surgical transection 3 days after axotomy (3 days distal)], heart, lung, thymus, spleen, liver, stomach, large intestine, kidney, testis, skin from the dorsum of the hind foot and gastrocnemius/soleus muscle with primers hybridizing to sequences in the amino terminus and the transmembrane domains of the GGF's.

EXAMPLE 33

In situ Hybridization Analysis of GGF Expression

A sciatic nerve, lumbar DRG, and the lumbar enlargement of the spinal cord were surgically transected from anesthetized adult male Harlan Sprague-Dawley rats. The tissues were fixed and eight micron cryosections were prepared as previously described (Carroll et al., 1992). Sense and antisense ³³P-labeled riboprobes were transcribed from plasmids pSLC123 (encoding NRG EGF-like common, EGF-like β and 1 juxtamembrane domains) and pSLC111 (encoding the NRG immunoglobulin-like domain) and in situ hybridizations were performed.

EXAMPLE 34

Secretion of Functional GGF Isoforms

Chinese hamster ovary (CHO) cells expressing GGF isoforms secrete functional NRG into their media. Monolayers of MCF-7 breast carcinoma cells were serum-starved and then challenged for 15 minutes with serum-free medium alone, serum-free media with 0.1% bovine serum albumin (BSA), 10 nM bacterially produced NRGβ1₁₆₈₋₂₃₇ or conditioned medium from four cell lines stably transfected with plasmids directing the expression of either GGFβ1a or GGFβ3. Cell lysates were prepared from these lysates, immunoblotted and probed with a rabbit polyclonal antiphosphotyrosine anti body. A 185 kD band was detected in lysates of cells stimulated with NRGβ1₁₆₈₋₂₃₇ or media conditioned by each of the GGF expressing cell lines, but not from cells challenged with serum-free medium alone or containing 0.1% BSA.GGF expression plasmids for GGFβ1a or GGFβ3 were transfected into a CHO line, and cell lines stably transfected with the plasmids were selected. Medium from each cell lines was tested for the presence of functional GGF isoforms using the same MCF-7 assay as was used to detect functional SMDFβ1a. Monolayers of MCF-7 breast carcinoma cells were serum-starved and then challenged for 15 minutes with serum-free medium alone, serum-free media with 0.1% bovine serum albumin (BSA), 10 nM bacterially produced NRGβ1₁₆₈₋₂₃₇ or conditioned medium from four cell lines stably expressing GGFβ1a or GGFβ3. Cell lysates were prepared from these lysates, immunoblotted and probed with a rabbit polyclonal antiphosphotyrosine antibody. A 185 kD band was detected in lysates of cells stimulated with NRGβ1₁₆₈₋₂₃₇ or media conditioned by each of the GGF expressing cell lines, but not from cells challenged with serum-free medium alone or containing 0.1% BSA.

EXAMPLE 35

Comparison of the Structures of SMDF and GGF Neuregulins

In spite of the structural complexity of the NRGs, all of these proteins share an EGF-like domain. The EGF-like domain, which consists of a common region fused to either α- or β-domains, is essential for biologic activity. Truncated β-NRG molecules containing only the EGF-like domain bind to the NRG receptor with an affinity similar to that of the full-length factor (Holmes et al., 1992; Peles et al., 1993) and are capable of inducing a variety of biologic responses (Holmes et al., 1992; Peles et al., 1993; Chu et al., 1995; Levi et al., 1995; Syroid et al., 1996). In spite of their similar structures, NRG α and β EGF-like domains are not functionally equivalent; β-NRGs have an affinity for erbB receptors an order of magnitude greater than α-NRGs (Wen et al., 1994). Furthermore, α-NRGs are nonmitogenic for some, but not all, cell types which proliferate in response to β-NRGs (Pinkas-Kramarski et al., 1996).

Other domains within the neuregulins are also structurally and functionally variable. In addition to the unique amino termini noted above (for which functions are currently unknown), the mesenchymal and GGF (but not the SMDF) neuregulin subfamilies contain an immunoglobulin-like domain (Ben-Baruch and Yarden, 1994; Peles and Yarden, 1993; Ho et al., 1995) mediating NRG interactions with cell surface glycoproteins, with resultant concentration and specific localization of the factor (Sudhalter et al., 1996). Splice variants in the GGF and mesenchymal neuregulin subfamilies also may contain serine and threonine-rich spacer domains which serve as the site of o- and n-linked glycosylation (Wen et al., 1994; Carroll et al., 1997); this glycosylation is non-essential for biologic activity and the precise function(s) of this region is as yet unknown.

NRGs may be synthesized as either transmembrane precursors or directly secretable forms. This distinction depends upon the juxtamembrane domain, which is immediately C terminal to the EGF-like domain. Four juxtamembrane domains, designated 1 to 4, have been identified in the rat. In this regard, the ‘3’ juxtamembrane domain is notable in that it, unlike other juxtamembrane domains, contains a termination codon, thus leading to truncation of the factor and synthesis in a directly secretable form. In all other NRG isoforms, the juxtamembrane domain is followed by a transmembrane domain which anchors the factor in the cell membrane and is itself coupled to one of three possible cytoplasmic domains (designated a, b, and c) (Wen et al., 1994). The cytoplasmic domains are highly conserved between species, suggesting an essential function (Wen et al., 1994); indeed, it has been recently reported that neuregulin cytoplasmic domains bind LIM kinase 1, suggesting that NRG transmembrane precursors are capable of transmitting signals into the interior of the cell synthesizing these proteins (Wang et al., 1998).

Discussion

The neuregulins and their erbb receptors are widely expressed in the developing and adult nervous system, suggesting that these molecules perform multiple essential functions in the brain and associated tissues. Neuregulins act on both CNS and PNS glia, although their actions on Schwann cells are at present better defined. The neuregulins have been implicated as neuronally synthesized, axon-associated signals influencing Schwann cell differentiation, survival and proliferation at multiple stage s in their development. Neuregulins direct neural crest cell differentiation into Schwann cells (Shah et al., 1994) and act on the Schwann cell precursor, an intermediate cell type arising from neural crest cells. Schwann cell precursors undergo apoptosis if not in contact with axons; neuregulins prevent axotomy-induced apoptosis of both Schwann cell precursors and neonatal Schwann cells surrounding neuromuscular junctions (Dong et al., 1995; Lee et al., 1995; Marchionni, 1995; Trachtenberg and Thompson, 1996; Lee et al., 1995; Marchionni, 1995; Trachtenberg and Thompson, 1996). Furthermore, neuregulins and erbB2 represent components of the “axon-associated mitogen” associated with neonatal sensory neuron axons (Morrissey et al., 1995), an observation consistent with the ability of members of the GGF and mesenchymal neuregulin subfamilies to stimulate proliferation of neonatal Schwann cells in vitro (Porter et al., 1986; Raff et al., 1978; Raabe et al., 1996).

Considered together, these observations have led to the concept of neuregulins as an axon-associated factor influencing Schwann cell differentiation, survival and proliferation during development (Lemke, 1996; Topilko et al., 1996; Lemke, 1996). However, this hypothesis may have to be modified in light of the finding that neonatal rat Schwann cells synthesize and secrete neuregulins in vitro (Raabe et al., 1996). Furthermore, Schwann cell expression of neuregulins is induced in adult rat sciatic nerve following axotomy (Carroll et al., 1997).

Neuregulins expressed by CNS neurons may also act as axon-associated factors regulating oligodendrocyte differentiation and survival (Vartanian et al., 1997). Both ARIA and GGF neuregulin isoforms act on developing oligodendrocytes, although the reported effects of these two isoforms differ from one another. ARIA acts to enhance oligodendrocyte differentiation from O2A progenitor cells without promoting proliferation (Vartanian et al., 1994). In contrast, Canoll et al. (Canoll et al., 1996) have reported that GGF inhibits differentiation and lineage commitment of oligodendroglial progenitors while acting as a mitogen for pro-oligodendrocytes, oligodendrocytes and type-2 astrocytes. Additionally, neonatal oligodendrocytes can be rescued from an apoptotic death by β- or α-neuregulin isoforms (Raabe et al., 1997). However, in an interesting parallel to the findings described above for Schwann cells, cultured oligodendrocytes have also been found to be capable of secreting neuregulin proteins themselves (Raabe et al., 1997). It is thus apparent that this class of glial cells is also capable of both responding to and secreting neuregulins.

Neuregulins have multiple actions on developing neurons, some of which are the result of direct actions of neuregulins on these cells and others which are indirectly mediated by neighboring glia. Verdi et al (Verdi et al., 1996) have demonstrated that the survival and development of sympathetic neuroblasts is indirectly mediated by neuronally produced neuregulin which is released, subsequently stimulating neurotrophin-3 release from adjacent ganglionic satellite cells. Neuregulins also promote maintenance and elongation of radial glia in the developing cortex (Anton et al., 1997) and cerebellum (Rio et al., 1997) and stimulate neuroblast migration along these glia.

Neuregulins may influence neuronal morphology and synaptic function. The GGFβ3 neuregulin isoform promotes survival and neurite extension in cultures of embryonic and neonatal rat retinal neurons (Bermingham-McDonogh et al., 1996). Neuregulins also stimulate functional expression of calcium-activated potassium channels in developing chick parasympathetic neurons (Subramony and Dryer, 1997) and increase neuronal expression of neurotransmitter receptors including NMDA (Ozaki et al., 1997) and nicotinic acetylcholine (Yang et al., 1998) receptor subunits. Although in some of these examples it is still unclear whether in vitro neuregulin effects result from neuregulins acting directly through the erbB receptors widely expressed by neurons throughout the nervous system (Pinkas-Kramarski et al., 1997; Burden and Yarden, 1997) or are mediated indirectly by contaminating glia, it is nonetheless clear that these factors have profound effects on multiple aspects of neuronal biology.

To test this hypothesis, it is necessary to first understand the range of structural and functional diversity of neuregulin isoforms expressed by neurons and glia. This study was therefore performed as an initial assessment of the structural and functional heterogenity of the SMDF subfamily, the predominant neuregulin isoforms expressed in many regions of the nervous system. It was previously reported that SMDF transcripts are undetectable in Northern blots of total cytoplasmic RNA isolated from noninjured adult rat sciatic nerve and sciatic nerve 7 days postaxotomy (Carroll et al., 1997). However, Ratner and colleagues subsequently found that SMDF mRNA is detectable in early postnatal rat sciatic nerve using highly sensitive RT-PCR analyses (Rosenbaum et al., 1997). These observations, considered together with the isolation of SMDF cDNAs from the JS1 schwannoma cell line described herein (see above), raise the question of whether earlier failures to detect SMDF mRNA in noninjured or axotomized adult peripheral nerve could be the result of the relative insensitivity of Northern blot analyses with total cytoplasmic RNA.

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Any patents or publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. These patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.

One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The present examples along with the methods, procedures, treatments, molecules, and specific compounds described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention as defined by the scope of the claims.

27 1 2856 DNA Rattus norvegicus Nucleotide sequence SMDF (1a cDNA (from clone pSLC135) 1 gaattcggca cgaggcgatg ctcagagggc aggcacctgc tgctctgtaa tgattcagcc 60 tctttcagcc gctgcgttaa cacgacagga tgctgttgct actgtcgctg ctgcctctcc 120 tgccgccgcc gctgctgccg ccgccgcctc ctctggtctt gcttttgctt ttacttctcc 180 tgcatgacag ttgttttctt cctctaagca gacaccagct tcagacgctt gaggtgagaa 240 acatgccttt cagtttggga tactggttta cttaatcggc taggcggcag cttgcttcct 300 attttggtcc cctgccttct tgaccaaccc ggcatggttt ggagaagcat ttgaaagaac 360 tgaaaaagtg tcccagaaac aacagctcaa gatatttcgg tacacttcta tttcatagtt 420 gctagaagcc ctttcttttt cgtttttttt ttctttttct ttttcttttt ctttttcctt 480 ttcctgcttc ctcctaagct ctggtacttt gggtaattgc cttggacttg ggtgccttat 540 cgatttcccc ctccaagatg ctgtatcatt tggttggggg gagctctgcg tggtaatgca 600 ctgtgagaga ggccaggcct tctggaggtg agccgatgga gatttattcc ccagacatgt 660 ctgaggtagc tggcgggagg tcctccagcc cctccactca gctgagtgca gccccatctc 720 ttgatgggct tccggcagcg gaggaacata taccagacac ccacacagaa gatgagagaa 780 gccctggact cctgggcctg gcggtgccct gctgtgtgtg cctggaagct gagcgcctga 840 gagggtgtct caactccgag aagatctgca ttgttcccat tctggcttgc ctagtcagcc 900 tctgcctctg cattgctggc ctgaagtggg tatttgtgga caagatattt gaatacgact 960 ctcctaccca ccttgaccct ggggggttag gccaggaccc tgtgatttct ctggatccaa 1020 ctgctgcccc agccattttg gtatcatctg aggcatacac ttcacctgtc tctaaggctc 1080 agtctgaagc tggggctcat gttacagtac aaggtgacca tgctgctgtg gcctctgaac 1140 cttcagcagt accgacccgg aagaaccggc tgtctgcttt tcctcccttt cactctactg 1200 caccgccctt cccttctcca gctcggaccc ctgaggtgag aacacccaag tcaggaactc 1260 agccacaaac aacagaaact aacctgcaaa ctgctcctaa actttccaca tcgacatcca 1320 cgactgggac cagccatctc ataaagtgcg cggagaagga gaaaactttc tgtgtgaatg 1380 ggggcgagtg cttcacggtg aaggacctgt caaacccgtc aagatacttg tgcaagtgcc 1440 caaatgagtt tactggtgat cgttgccaaa actacgtaat ggccagcttc tacaagcatc 1500 ttgggattga atttatggaa gcggaggaac tctaccagaa gagggtgctg acaattactg 1560 gcatctgtat cgccctgctg gtggtcggca tcatgtgtgt ggtggcctac tgcaaaacca 1620 agaagcagcg gcagaagctt catgatcggc ttcggcagag tcttcggtca gaacggagca 1680 acctggtgaa catagcgaat gggcctcacc acccaaaccc gccgccagag aacgtgcagc 1740 tggtgaatca atacgtatct aaaaacgtca tctccagtga gcatattgtt gagagagaag 1800 tggagacttc cttttccacc agtcattaca cttccacagc ccatcactcc acgactgtca 1860 cccagactcc tagtcacagc tggagtaatg ggcacacgga gagcgtcatt tcagaaagca 1920 actccgtaat catgatgtct tcggtagaga acagcaggca cagcagtccc gccgggggcc 1980 cacgaggacg tcttcatggc ctgggaggcc ctcgtgataa cagcttcctc aggcatgcca 2040 gagaaacccc tgactcctac agagactctc ctcatagcga aaggtatgta tcagccatga 2100 ccaccccggc tcgtatgtca cctgtagatt tccacacgcc aagctcccct aaatcgcccc 2160 cttcggaaat gtctccaccc gtgtccagca tgacggtgtc catgccctct gtggcagtca 2220 gcccctttgt ggaagaagag aggcctctgc tgcttgtgac gccaccaagg ctacgggaga 2280 agaaatatga tcatcacccc cagcaactca actcctttca tcacaaccct gcacatcaga 2340 gtaccagcct cccccctagc ccactgagga tagtggagga tgaggagtac gagacgaccc 2400 aggagtatga gtcagttcaa gagcccgtta agaaagtcac caatagccgg cgggccaaaa 2460 gaaccaagcc caatggccac attgccaata ggttggaaat ggacagcaac acaagttctg 2520 tgagcagtaa ctcagaaagt gagacagaag acgaaagagt aggtgaagac acaccattcc 2580 tgggcataca gaaccccctg gcagccagcc ttgaggtggc ccccgccttc cgtctggctg 2640 agagcaggac taacccagca ggccgcttct ccacacagga ggaattacag gccaggctgt 2700 ctagtgtaat cgctaaccaa gaccctattg ctgtataaaa cctaaataaa cacatagatt 2760 cacctgtaaa actttatttt atataataaa gtatttcacc ttaaattaaa caatttattt 2820 tattttagca gttctgcaaa tactcgtgcc gaattc 2856 2 700 PRT Rattus norvegicus Amino acid sequence of SMDF(1a (encoded by clone pSLC135) 2 Met Glu Ile Tyr Ser Pro Asp Met Ser Glu Val Ala Gly Gly Arg 5 10 15 Ser Ser Ser Pro Ser Thr Gln Leu Ser Ala Ala Pro Ser Leu Asp 20 25 30 Gly Leu Pro Ala Ala Glu Glu His Ile Pro Asp Thr His Thr Glu 35 40 45 Asp Glu Arg Ser Pro Gly Leu Leu Gly Leu Ala Val Pro Cys Cys 50 55 60 Val Cys Leu Glu Ala Glu Arg Leu Arg Gly Cys Leu Asn Ser Glu 65 70 75 Lys Ile Cys Ile Val Pro Ile Leu Ala Cys Leu Val Ser Leu Cys 80 85 90 Leu Cys Ile Ala Gly Leu Lys Trp Val Phe Val Asp Lys Ile Phe 95 100 105 Glu Tyr Asp Ser Pro Thr His Leu Asp Pro Gly Gly Leu Gly Gln 110 115 120 Asp Pro Val Ile Ser Leu Asp Pro Thr Ala Ala Pro Ala Ile Leu 125 130 135 Val Ser Ser Glu Ala Tyr Thr Ser Pro Val Ser Lys Ala Gln Ser 140 145 150 Glu Ala Gly Ala His Val Thr Val Gln Gly Asp His Ala Ala Val 155 160 165 Ala Ser Glu Pro Ser Ala Val Pro Thr Arg Lys Asn Arg Leu Ser 170 175 180 Ala Phe Pro Pro Phe His Ser Thr Ala Pro Pro Phe Pro Ser Pro 185 190 195 Ala Arg Thr Pro Glu Val Arg Thr Pro Lys Ser Gly Thr Gln Pro 200 205 210 Gln Thr Thr Glu Thr Asn Leu Gln Thr Ala Pro Lys Leu Ser Thr 215 220 225 Ser Thr Ser Thr Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu 230 235 240 Lys Glu Lys Thr Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val 245 250 255 Lys Asp Leu Ser Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn 260 265 270 Glu Phe Thr Gly Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe 275 280 285 Tyr Lys His Leu Gly Ile Glu Phe Met Glu Ala Glu Glu Leu Tyr 290 295 300 Gln Lys Arg Val Leu Thr Ile Thr Gly Ile Cys Ile Ala Leu Leu 305 310 315 Val Val Gly Ile Met Cys Val Val Ala Tyr Cys Lys Thr Lys Lys 320 325 330 Gln Arg Gln Lys Leu His Asp Arg Leu Arg Gln Ser Leu Arg Ser 335 340 345 Glu Arg Ser Asn Leu Val Asn Ile Ala Asn Gly Pro His His Pro 350 355 360 Asn Pro Pro Pro Glu Asn Val Gln Leu Val Asn Gln Tyr Val Ser 365 370 375 Lys Asn Val Ile Ser Ser Glu His Ile Val Glu Arg Glu Val Glu 380 385 390 Thr Ser Phe Ser Thr Ser His Tyr Thr Ser Thr Ala His His Ser 395 400 405 Thr Thr Val Thr Gln Thr Pro Ser His Ser Trp Ser Asn Gly His 410 415 420 Thr Glu Ser Val Ile Ser Glu Ser Asn Ser Val Ile Met Met Ser 425 430 435 Ser Val Glu Asn Ser Arg His Ser Ser Pro Ala Gly Gly Pro Arg 440 445 450 Gly Arg Leu His Gly Leu Gly Gly Pro Arg Asp Asn Ser Phe Leu 455 460 465 Arg His Ala Arg Glu Thr Pro Asp Ser Tyr Arg Asp Ser Pro His 470 475 480 Ser Glu Arg Tyr Val Ser Ala Met Thr Thr Pro Ala Arg Met Ser 485 490 495 Pro Val Asp Phe His Thr Pro Ser Ser Pro Lys Ser Pro Pro Ser 500 505 510 Glu Met Ser Pro Pro Val Ser Ser Met Thr Val Ser Met Pro Ser 515 520 525 Val Ala Val Ser Pro Phe Val Glu Glu Glu Arg Pro Leu Leu Leu 530 535 540 Val Thr Pro Pro Arg Leu Arg Glu Lys Lys Tyr Asp His His Pro 545 550 555 Gln Gln Leu Asn Ser Phe His His Asn Pro Ala His Gln Ser Thr 560 565 570 Ser Leu Pro Pro Ser Pro Leu Arg Ile Val Glu Asp Glu Glu Tyr 575 580 585 Glu Thr Thr Gln Glu Tyr Glu Ser Val Gln Glu Pro Val Lys Lys 590 595 600 Val Thr Asn Ser Arg Arg Ala Lys Arg Thr Lys Pro Asn Gly His 605 610 615 Ile Ala Asn Arg Leu Glu Met Asp Ser Asn Thr Ser Ser Val Ser 620 625 630 Ser Asn Ser Glu Ser Glu Thr Glu Asp Glu Arg Val Gly Glu Asp 635 640 645 Thr Pro Phe Leu Gly Ile Gln Asn Pro Leu Ala Ala Ser Leu Glu 650 655 660 Val Ala Pro Ala Phe Arg Leu Ala Glu Ser Arg Thr Asn Pro Ala 665 670 675 Gly Arg Phe Ser Thr Gln Glu Glu Leu Gln Ala Arg Leu Ser Ser 680 685 690 Val Ile Ala Asn Gln Asp Pro Ile Ala Val 695 700 3 296 PRT Homo sapiens Amino acid sequence of human SMDF(3 3 Met Glu Ile Tyr Ser Pro Asp Met Ser Glu Val Ala Ala Glu Arg 5 10 15 Ser Ser Ser Pro Ser Thr Gln Leu Ser Ala Asp Pro Ser Leu Asp 20 25 30 Gly Leu Pro Ala Ala Glu Asp Met Pro Glu Pro Gln Thr Glu Asp 35 40 45 Gly Arg Thr Pro Gly Leu Val Gly Leu Ala Val Pro Cys Cys Ala 50 55 60 Cys Leu Glu Ala Glu Arg Leu Arg Gly Cys Leu Asn Ser Glu Lys 65 70 75 Ile Cys Ile Val Pro Ile Leu Ala Cys Leu Val Ser Leu Cys Leu 80 85 90 Cys Ile Ala Gly Leu Lys Trp Val Phe Val Asp Lys Ile Phe Glu 95 100 105 Tyr Asp Ser Pro Thr His Leu Asp Pro Gly Gly Leu Gly Gln Asp 110 115 120 Pro Ile Ile Ser Leu Asp Ala Thr Ala Ala Ser Ala Val Trp Val 125 130 135 Ser Ser Glu Ala Tyr Thr Ser Pro Val Ser Arg Ala Gln Ser Glu 140 145 150 Ser Glu Val Gln Val Thr Val Gln Gly Asp Lys Ala Val Val Ser 155 160 165 Phe Glu Pro Ser Ala Ala Pro Thr Pro Lys Asn Arg Ile Phe Ala 170 175 180 Phe Ser Phe Leu Pro Ser Thr Ala Pro Ser Phe Pro Ser Pro Thr 185 190 195 Arg Asn Pro Glu Val Arg Thr Pro Lys Ser Ala Thr Gln Pro Gln 200 205 210 Thr Thr Glu Thr Asn Leu Gln Thr Ala Pro Lys Leu Ser Thr Ser 215 220 225 Thr Ser Thr Thr Gly Thr Ser His Leu Val Lys Cys Ala Glu Lys 230 235 240 Glu Lys Thr Phe Cys Val Asn Gly Gly Glu Cys Phe Met Val Lys 245 250 255 Asp Leu Ser Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn Glu 260 265 270 Phe Thr Gly Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe Tyr 275 280 285 Ser Thr Ser Thr Pro Phe Leu Ser Leu Pro Glu 290 295 4 2540 DNA Rattus norvegicus CDS 370..2458 SMDF_2a amino acid sequence 4 gaattcggca cgaggcggca gcttgcttcc tattttggtc ccctgccttc ttgaccaacc 60 cggcatggtt tggagaagca tttgaaagaa ctgaaaaagt gtcccagaaa caacagctca 120 agatatttcg gtacacttct atttcatagt tgctagaagc cctttctttt ttcgtttttt 180 ttttttcttt ttctttttct ttttcttttt ccttttcctg cttcctccta agctctggta 240 ctttgggtaa ttgccttgga cttgggtgcc ttatcgattt ccccctccaa gatgctgtat 300 catttggttg gggggagctc tgcgtggtaa tgcactgtga gagaggccag gccttctgga 360 ggtgagccga tggagattta ttccccagac atgtctgagg tagctggcgg gaggtcctcc 420 agcccctcca ctcagctgag tgcagttcca tctcttgatg ggcttccggc agcggaggaa 480 catataccag acacccacac agaagatgag agaagccctg gactcctggg cctggcggtg 540 ccctgctgtg tgtgcctgga agctgagcgc ctgagagggt gtctcaactc cgagaagatc 600 tgcattgttc ccattctggc ttgcctagtc agcctctgcc tctgcattgc tggcctgaag 660 tgggtatttg tggacaagat atttgaatac gactctccta cccaccttga ccctgggggg 720 ttaggccagg accctgtgat ttctctggat ccaactgctg ccccagccat tttggtatca 780 tccgaggcat acacttcacc tgtctctaag gctcagtctg aagctggggc tcatgttaca 840 gtacaaggtg accatgctgc tgtggcctct gaaccttcag cagtaccgac ccggaagaac 900 cggctgtctg cttttcctcc ctttcaccct actgcaccgc ccttcccttc tccagctcgg 960 acccctgagg tgagaacacc caagtcagga actcagccac aaacaacaga aactaacctg 1020 caaactgctc ctaaactttc cacatcaaca tccacgactg ggaccagcca tctcataaag 1080 tgtgcggaga aggagaaaac tttctgtgtg aatgggggcg agtgcttcac ggtgaaggac 1140 ctgtcaaacc cgtcaagata cttgtgcaag tgccaacctg gattcactgg agcaagatgt 1200 actgagaatg tacccatgaa agtccaaacc caagaaaaag cggaggaact ctaccagaag 1260 agggtgctga caattactgg catctgtatc gccctgctgg tggtcggcat catgtgtgtg 1320 gtggcctact gcaaaaccaa gaagcagcgg cagaagcttc atgatcggct tcggcagagt 1380 cttcggtcag aacggagcaa cctggtgaac atagcgaatg ggcctcacca cccaaacccg 1440 ccgccagaga acgtgcagct ggtgaatcaa tacgtatcta aaaacgtcat ctccagtgag 1500 catattgttg agagagaagt ggagacttcc ttttccacca gtcattacac ttccacagcc 1560 catcactcca cgactgtcac ccagactcct agtcacagct ggagtaatgg gcacacggag 1620 agcgtcattt cagaaagcaa ctccgtaatc atgatgtctt cggtagagaa cagcaggcac 1680 agcagtcccg ccgggggccc acgaggacgt cttcatggcc tgggaggccc tcgtgataac 1740 agcttcctca ggcatgccag agaaacccct gactcctaca gagactctcc tcatagcgaa 1800 aggtatgtat cagccatgac caccccggct cgtatgtcac ctgtagattt ccacacgcca 1860 agctccccta aatcgccccc ttcggaaatg tctccacccg tgtccagcat gacggtgtcc 1920 atgccctctg tggcagtcag cccctttgtg gaagaagaga ggcctctgct gcttgtgacg 1980 ccaccaaggc tacgggagaa gaaatatgat catcaccccc agcaactcaa ctcctttcat 2040 cacaaccctg cacatcagag taccagcctc ccccctagcc cactgaggat agtggaggat 2100 gaggagtacg agacgaccca ggagtatgag tcagttcaag agcccgttaa gaaagtcacc 2160 aatagccggc gggccaaaag aaccaagccc aatggccaca ttgccaatag gttggaaatg 2220 gacagcaaca caagttctgt gagcagtaac tcagaaagtg agacagaaga cgaaagagta 2280 ggtgaagaca caccattcct gggcatacag aaccccctgg cagccagcct tgaggtggcc 2340 cccgccttcc gtctggctga gagcaggact aacccagcag gccgcttctc cacacaggag 2400 gaattacagg ccaggctgtc tagtgtaatc gctaaccaag accctattgc tgtataaaac 2460 ctaaataaac acatagattc acctgtaaaa ctttatttta tataataaag tatttcacct 2520 taaaaaaaaa aaaaaaaaaa 2540 5 695 PRT Rattus norvegicus SMDF_2a amino acid sequence 5 Met Glu Ile Tyr Ser Pro Asp Met Ser Glu Val Ala Gly Gly Arg 5 10 15 Ser Ser Ser Pro Ser Thr Gln Leu Ser Ala Val Pro Ser Leu Asp 20 25 30 Gly Leu Pro Ala Ala Glu Glu His Ile Pro Asp Thr His Thr Glu 35 40 45 Asp Glu Arg Ser Pro Gly Leu Leu Gly Leu Ala Val Pro Cys Cys 50 55 60 Val Cys Leu Glu Ala Glu Arg Leu Arg Gly Cys Leu Asn Ser Glu 65 70 75 Lys Ile Cys Ile Val Pro Ile Leu Ala Cys Leu Val Ser Leu Cys 80 85 90 Leu Cys Ile Ala Gly Leu Lys Trp Val Phe Val Asp Lys Ile Phe 95 100 105 Glu Tyr Asp Ser Pro Thr His Leu Asp Pro Gly Gly Leu Gly Gln 110 115 120 Asp Pro Val Ile Ser Leu Asp Pro Thr Ala Ala Pro Ala Ile Leu 125 130 135 Val Ser Ser Glu Ala Tyr Thr Ser Pro Val Ser Lys Ala Gln Ser 140 145 150 Glu Ala Gly Ala His Val Thr Val Gln Gly Asp His Ala Ala Val 155 160 165 Ala Ser Glu Pro Ser Ala Val Pro Thr Arg Lys Asn Arg Leu Ser 170 175 180 Ala Phe Pro Pro Phe His Pro Thr Ala Pro Pro Phe Pro Ser Pro 185 190 195 Ala Arg Thr Pro Glu Val Arg Thr Pro Lys Ser Gly Thr Gln Pro 200 205 210 Gln Thr Thr Glu Thr Asn Leu Gln Thr Ala Pro Lys Leu Ser Thr 215 220 225 Ser Thr Ser Thr Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu 230 235 240 Lys Glu Lys Thr Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val 245 250 255 Lys Asp Leu Ser Asn Pro Ser Arg Tyr Leu Cys Lys Cys Gln Pro 260 265 270 Gly Phe Thr Gly Ala Arg Cys Thr Glu Asn Val Pro Met Lys Val 275 280 285 Gln Thr Gln Glu Lys Ala Glu Glu Leu Tyr Gln Lys Arg Val Leu 290 295 300 Thr Ile Thr Gly Ile Cys Ile Ala Leu Leu Val Val Gly Ile Met 305 310 315 Cys Val Val Ala Tyr Cys Lys Thr Lys Lys Gln Arg Gln Lys Leu 320 325 330 His Asp Arg Leu Arg Gln Ser Leu Arg Ser Glu Arg Ser Asn Leu 335 340 345 Val Asn Ile Ala Asn Gly Pro His His Pro Asn Pro Pro Pro Glu 350 355 360 Asn Val Gln Leu Val Asn Gln Tyr Val Ser Lys Asn Val Ile Ser 365 370 375 Ser Glu His Ile Val Glu Arg Glu Val Glu Thr Ser Phe Ser Thr 380 385 390 Ser His Tyr Thr Ser Thr Ala His His Ser Thr Thr Val Thr Gln 395 400 405 Thr Pro Ser His Ser Trp Ser Asn Gly His Thr Glu Ser Val Ile 410 415 420 Ser Glu Ser Asn Ser Val Ile Met Met Ser Ser Val Glu Asn Ser 425 430 435 Arg His Ser Ser Pro Ala Gly Gly Pro Arg Gly Arg Leu His Gly 440 445 450 Leu Gly Gly Pro Arg Asp Asn Ser Phe Leu Arg His Ala Arg Glu 455 460 465 Thr Pro Asp Ser Tyr Arg Asp Ser Pro His Ser Glu Arg Tyr Val 470 475 480 Ser Ala Met Thr Thr Pro Ala Arg Met Ser Pro Val Asp Phe His 485 490 495 Thr Pro Ser Ser Pro Lys Ser Pro Pro Ser Glu Met Ser Pro Pro 500 505 510 Val Ser Ser Met Thr Val Ser Met Pro Ser Val Ala Val Ser Pro 515 520 525 Phe Val Glu Glu Glu Arg Pro Leu Leu Leu Val Thr Pro Pro Arg 530 535 540 Leu Arg Glu Lys Lys Tyr Asp His His Pro Gln Gln Leu Asn Ser 545 550 555 Phe His His Asn Pro Ala His Gln Ser Thr Ser Leu Pro Pro Ser 560 565 570 Pro Leu Arg Ile Val Glu Asp Glu Glu Tyr Glu Thr Thr Gln Glu 575 580 585 Tyr Glu Ser Val Gln Glu Pro Val Lys Lys Val Thr Asn Ser Arg 590 595 600 Arg Ala Lys Arg Thr Lys Pro Asn Gly His Ile Ala Asn Arg Leu 605 610 615 Glu Met Asp Ser Asn Thr Ser Ser Val Ser Ser Asn Ser Glu Ser 620 625 630 Glu Thr Glu Asp Glu Arg Val Gly Glu Asp Thr Pro Phe Leu Gly 635 640 645 Ile Gln Asn Pro Leu Ala Ala Ser Leu Glu Val Ala Pro Ala Phe 650 655 660 Arg Leu Ala Glu Ser Arg Thr Asn Pro Ala Gly Arg Phe Ser Thr 665 670 675 Gln Glu Glu Leu Gln Ala Arg Leu Ser Ser Val Ile Ala Asn Gln 680 685 690 Asp Pro Ile Ala Val 695 6 897 DNA Rattus norvegicus Partial cDNA sequence of SMDF_2b 6 actctactgc accgcccttc ccttctccag ctcggacccc tgaggtgaga acacccaagt 60 caggaactca gccacaaaca acagaaacta acctgcaaac tgctcctaaa ctttccacat 120 caacatccac gactgggacc agccatctca taaagtgtgc ggagaaggag aaaactttct 180 gtgtgaatgg gggcgagtgc ttcacggtga aggacctgtc aaacccgtca agatacttgt 240 gcaagtgcca acctggattc actggagcaa gatgtactga gaatgtaccc atgaaagtcc 300 aaacccaaga aaaagcggag gaactctacc agaagagggt gctgacaatt actggcatct 360 gtatcgccct gctggtggtc ggcatcatgt gtgtggtggc ctactgcaaa accaagaagc 420 agcggcagaa gcttcatgat cggcttcggc agagtcttcg gtcagaacgg agcaacctgg 480 tgaacatagc gaatgggcct caccacccaa acccgccgcc agagaacgtg cagctggtga 540 atcaatacgt atctaaaaac gtcatctcca gtgagcatat tgttgagaga gaagtggaga 600 cttccttttc caccagtcat tacacttcca cagcccatca ctccacgact gtcacccaga 660 ctcctagtca cagctggagt aatgggcaca cggagagcgt catttcagaa agcaactccg 720 taatcatgat gtcttcggta gagaacagca ggcacagcag tcccgccggg ggcccacgag 780 gacgtcttca tggcctggga ggccctcgtg ataacagctt cctcaggcat gccagagaaa 840 cccctgactc ctacagagac tctcctcata gcgaaagaca taaccttata gctgagc 897 7 298 PRT Rattus norvegicus Partial amino acid sequence of SMDF_2b 7 Ser Thr Ala Pro Pro Phe Pro Ser Pro Ala Arg Thr Pro Glu Val 5 10 15 Arg Thr Pro Lys Ser Gly Thr Gln Pro Gln Thr Thr Glu Thr Asn 20 25 30 Leu Gln Thr Ala Pro Lys Leu Ser Thr Ser Thr Ser Thr Thr Gly 35 40 45 Thr Ser His Leu Ile Lys Cys Ala Glu Lys Glu Lys Thr Phe Cys 50 55 60 Val Asn Gly Gly Glu Cys Phe Thr Val Lys Asp Leu Ser Asn Pro 65 70 75 Ser Arg Tyr Leu Cys Lys Cys Gln Pro Gly Phe Thr Gly Ala Arg 80 85 90 Cys Thr Glu Asn Val Pro Met Lys Val Gln Thr Gln Glu Lys Ala 95 100 105 Glu Glu Leu Tyr Gln Lys Arg Val Leu Thr Ile Thr Gly Ile Cys 110 115 120 Ile Ala Leu Leu Val Val Gly Ile Met Cys Val Val Ala Tyr Cys 125 130 135 Lys Thr Lys Lys Gln Arg Gln Lys Leu His Asp Arg Leu Arg Gln 140 145 150 Ser Leu Arg Ser Glu Arg Ser Asn Leu Val Asn Ile Ala Asn Gly 155 160 165 Pro His His Pro Asn Pro Pro Pro Glu Asn Val Gln Leu Val Asn 170 175 180 Gln Tyr Val Ser Lys Asn Val Ile Ser Ser Glu His Ile Val Glu 185 190 195 Arg Glu Val Glu Thr Ser Phe Ser Thr Ser His Tyr Thr Ser Thr 200 205 210 Ala His His Ser Thr Thr Val Thr Gln Thr Pro Ser His Ser Trp 215 220 225 Ser Asn Gly His Thr Glu Ser Val Ile Ser Glu Ser Asn Ser Val 230 235 240 Ile Met Met Ser Ser Val Glu Asn Ser Arg His Ser Ser Pro Ala 245 250 255 Gly Gly Pro Arg Gly Arg Leu His Gly Leu Gly Gly Pro Arg Asp 260 265 270 Asn Ser Phe Leu Arg His Ala Arg Glu Thr Pro Asp Ser Tyr Arg 275 280 285 Asp Ser Pro His Ser Glu Arg His Asn Leu Ile Ala Glu 290 295 8 333 DNA Rattus norvegicus Partial cDNA sequence of SMDF_2 8 gcttttcctc cctttcactc tactgcaccg cccttccctt ctccagctcg gacccctgag 60 gtgagaacac ccaagtcagg aactcagcca caaacaacag aaactaacct gcaaactgct 120 cctaaacttt ccacaacaac atccacgact gggaccagcc atctcataaa gtgtgcggag 180 aaggagaaaa ctttctgtgt gaatgggggc gagtgcttca cggtgaagga cctgtcaaac 240 ccgtcaagat acttgtgcaa gtgcccaaat gagtttactg gtgatcgttg ccaaaactac 300 gtaatggcca gcttctacaa agcggaggaa ctc 333 9 111 PRT Rattus norvegicus Partial amino acid sequence of SMDF_2 9 Ala Phe Pro Pro Phe His Ser Thr Ala Pro Pro Phe Pro Ser Pro 5 10 15 Ala Arg Thr Pro Glu Val Arg Thr Pro Lys Ser Gly Thr Gln Pro 20 25 30 Gln Thr Thr Glu Thr Asn Leu Gln Thr Ala Pro Lys Leu Ser Thr 35 40 45 Thr Thr Ser Thr Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu 50 55 60 Lys Glu Lys Thr Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val 65 70 75 Lys Asp Leu Ser Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn 80 85 90 Glu Phe Thr Gly Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe 95 100 105 Tyr Lys Ala Glu Glu Leu 110 10 808 DNA Rattus norvegicus Partial cDNA sequence of SMDF_3 10 cacccacaca gaagatgaga gaagccctgg actcctgggc ctggcggtgc cctgctgtgt 60 gtgcctggaa gctgagcgcc tgagagggtg tctcaactcc gagaagatct gcattgttcc 120 cattctggct tgcctagtca gcctctgcct ctgcattgct ggcctgaagt gggtatttgt 180 ggacaagata tttgaatacg actctcctac ccaccttgac cctggggggt taggccagga 240 ccctgtgatt tctctggatc caactgctgc cccagccatt ttggtatcat ccgaggcata 300 cacttcacct gtctctaagg ctcagtctga agctggggct catgttacag tacaaggtga 360 ccatgctgct gtggcctctg aaccttcagc agtaccgacc cggaagaacc ggctgtctgc 420 ttttcctccc tttcactcta ctgcaccgcc cttcccttct ccagctcgga cccctgaagt 480 gagaacaccc aagtcaggaa ctcagccaca aacaacagaa actaacctgc aaactgctcc 540 taaactttcc acatcaacat ccacgactgg gaccagccat ctcataaagt gtgcggagaa 600 ggagaaaact ttctgtgtga atgggggcga gtgcttcacg gtgaaggacc tgtcaaaccc 660 gtcaagatac ttgtgcaagt gcccaaatga gtttactggt gatcgttgcc aaaactacgt 720 aatggccagc ttctacagta cgtccactcc ctttctgtct ctgcctgagt aggagcatgc 780 tcagtcgatg ctgctttctt gttgctac 808 11 256 PRT Rattus norvegicus Partial amino acid sequence of SMDF_3 11 Thr His Thr Glu Asp Glu Arg Ser Pro Gly Leu Leu Gly Leu Ala 5 10 15 Val Pro Cys Cys Val Cys Leu Glu Ala Glu Arg Leu Arg Gly Cys 20 25 30 Leu Asn Ser Glu Lys Ile Cys Ile Val Pro Ile Leu Ala Cys Leu 35 40 45 Val Ser Leu Cys Leu Cys Ile Ala Gly Leu Lys Trp Val Phe Val 50 55 60 Asp Lys Ile Phe Glu Tyr Asp Ser Pro Thr His Leu Asp Pro Gly 65 70 75 Gly Leu Gly Gln Asp Pro Val Ile Ser Leu Asp Pro Thr Ala Ala 80 85 90 Pro Ala Ile Leu Val Ser Ser Glu Ala Tyr Thr Ser Pro Val Ser 95 100 105 Lys Ala Gln Ser Glu Ala Gly Ala His Val Thr Val Gln Gly Asp 110 115 120 His Ala Ala Val Ala Ser Glu Pro Ser Ala Val Pro Thr Arg Lys 125 130 135 Asn Arg Leu Ser Ala Phe Pro Pro Phe His Ser Thr Ala Pro Pro 140 145 150 Phe Pro Ser Pro Ala Arg Thr Pro Glu Val Arg Thr Pro Lys Ser 155 160 165 Gly Thr Gln Pro Gln Thr Thr Glu Thr Asn Leu Gln Thr Ala Pro 170 175 180 Lys Leu Ser Thr Ser Thr Ser Thr Thr Gly Thr Ser His Leu Ile 185 190 195 Lys Cys Ala Glu Lys Glu Lys Thr Phe Cys Val Asn Gly Gly Glu 200 205 210 Cys Phe Thr Val Lys Asp Leu Ser Asn Pro Ser Arg Tyr Leu Cys 215 220 225 Lys Cys Pro Asn Glu Phe Thr Gly Asp Arg Cys Gln Asn Tyr Val 230 235 240 Met Ala Ser Phe Tyr Ser Thr Ser Thr Pro Phe Leu Ser Leu Pro 245 250 255 Glu 12 408 DNA Rattus norvegicus Partial cDNA sequence of SMDF_4 12 gcttttcctc cctttcactc tactgcaccg cccttccctt ctccagctcg gacccctgag 60 gtgagaacac ccaagtcagg aactcagcca caaacaacag aaactaacct gcaaactgct 120 cctaaacttt ccacatcaac atccacgact gggaccagcc atctcataaa gtgtgcggag 180 aaggagaaaa ctttctgtgt gaatgggggc gagtgcttca cggtgaagga cctgtcaaac 240 ccgtcaagat acttgtgcaa gtgcccaaat gagtttactg gtgatcgttg ccaaaactac 300 gtaatggcca gcttctacat gacttctagg aggaaaaggc aagaaacaga gaagcctcta 360 gaaagaaaat tggatcatag ccttgtgaaa gaatcgaaag cggaggaa 408 13 136 PRT Rattus norvegicus Partial amino acid sequence of SMDF_4 13 Ala Phe Pro Pro Phe His Ser Thr Ala Pro Pro Phe Pro Ser Pro 5 10 15 Ala Arg Thr Pro Glu Val Arg Thr Pro Lys Ser Gly Thr Gln Pro 20 25 30 Gln Thr Thr Glu Thr Asn Leu Gln Thr Ala Pro Lys Leu Ser Thr 35 40 45 Ser Thr Ser Thr Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu 50 55 60 Lys Glu Lys Thr Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val 65 70 75 Lys Asp Leu Ser Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn 80 85 90 Glu Phe Thr Gly Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe 95 100 105 Tyr Met Thr Ser Arg Arg Lys Arg Gln Glu Thr Glu Lys Pro Leu 110 115 120 Glu Arg Lys Leu Asp His Ser Leu Val Lys Glu Ser Lys Ala Glu 125 130 135 Glu 14 21 DNA Artificial sequence Synthetic oligonucleotide corresponding to common SMDF amino terminus forward used for PCR of SMDF isoforms 14 tatgttcctc cgctgccgga a 21 15 18 DNA Artificial sequence Synthetic oligonucleotide used for PCR of SMDF isoforms 15 gcttttcctc cctttcac 18 16 21 DNA Artificial sequence Synthetic oligonucleotide used for PCR of SMDF isoforms 16 cacccacaca gaagatgaga g 21 17 23 DNA Artificial sequence Synthetic oligonucleotide for 5′ untranslated region of SMDF(1a cDNA (pSLC135) 17 cagacgcctg aggtgagaaa cat 23 18 24 DNA Artificial sequence Synthetic oligonucleotide for 5′ untranslated region of SMDF(1a cDNA (pSLC135) 18 aagtccaagg caattaccca aagt 24 19 6 DNA Unknown polyA_signal 1..6 eukaryotic polyadenylation signal 19 aataaa 6 20 3086 DNA Rattus norvegicus GGF_1a cDNA sequence 20 gaattcggca cgagcccagc gtgggctcgg tgcaggagct ggcccggcgc gccgcggtgg 60 tgatcgaggg aaaggtgcac ccgccgcggc ggcagcaggg ggcactcgac aggaaggcag 120 caggcgaggc aggggcaggg gcgcgggacc agcccgtcca ggactcgcca ccttcacagg 180 accctctgcc tgctgtcaac tggaccctgc ccactggggg ccccgagccc agcaccgatc 240 agcccgggga ccccgcgccc tatctggtca aggtgcacca ggtgtgggct gtgaaagccg 300 ggggtttgaa gaaggactcg ctactcaccg tgcgcctgga tacctggggc cacccagcct 360 tcccgtcctg cgggcggctc aaggaggaca gcaggtacat cttcttcatg gagccggatg 420 ccaacagcag cggccgcgcg ccgcccgcct tccgagcctc gtttccccca ctggagactg 480 gccgcaacct caagaaggag gtcagccggg tgttgtgcaa gcggtgcgca ctgcctccca 540 gattgaaaga aatgaagagc caggagtcag ctgcaggctc caagctagtg ctccggtgcg 600 aaaccagctc cgagtactcc tcactcagat tcaaatggtt caagaatggg aacgagctga 660 accgcaaaaa taaaccagaa aacatcaaga tacagaagaa gccagggaag tcagagcttc 720 gaattaacaa agcatccctg gctgactctg gagagtatat gtgcaaagtg atcagcaagt 780 taggaaatga cagtgcctct gccaacatca ccattgttga gtcaaacgag ttcatcactg 840 gcatgccagc ctcgactgag acagcctatg tgtcctcaga gtctcccatt agaatctcag 900 tttcaacaga aggcgcaaac acttcttcat ccacatcgac atccacgact gggaccagcc 960 atctcataaa gtgcgcggag aaggagaaaa ctttctgtgt gaatgggggc gagtgcttca 1020 cggtgaagga cctgtcaaac ccgtcaagat acttgtgcaa gtgcccaaat gagtttactg 1080 gtgatcgttg ccaaaactac gtaatggcca gcttctacaa gcatcttggg attgaattta 1140 tggaagcgga ggaactctac cagaagaggg tgctgacaat tactggcatc tgtatcgccc 1200 tgctggtggt cggcatcatg tgtgtggtgg cctactgcaa aaccaagaag cagcggcaga 1260 agcttcatga tcggcttcgg cagagtcttc ggtcagaacg gagcaacctg gtgaacatag 1320 cgaatgggcc tcaccaccca aacccgccgc cagagaacgt gcagctggtg aatcaatacg 1380 tatctaaaaa cgtcatctcc agtgagcata ttgttgagag agaagtggag acttcctttt 1440 ccaccagtca ttacacttcc acagcccatc actccacgac tgtcacccag actcctagtc 1500 acagctggag taatgggcac acggagagcg tcatttcaga aagcaactcc gtaatcatga 1560 tgtcttcggt agagaacagc aggcacagca gtcccgccgg gggcccacga ggacgtcttc 1620 atggcctggg aggccctcgt gataacagct tcctcaggca tgccagagaa acccctgact 1680 cctacagaga ctctcctcat agcgaaaggt atgtatcagc catgaccacc ccggctcgta 1740 tgtcacctgt agatttccac acgccaagct cccctaaatc gcccccttcg gaaatgtctc 1800 cacccgtgtc cagcatgacg gtgtccatgc cctctgtggc agtcagcccc tttgtggaag 1860 aagagaggcc tctgctgctt gtgacgccac caaggctacg ggagaagaaa tatgatcatc 1920 acccccagca actcaactcc tttcatcaca accctgcaca tcagagtacc agcctccccc 1980 ctagcccact gaggatagtg gaggatgagg agtacgagac gacccaggag tatgagtcag 2040 ttcaagagcc cgttaagaaa gtcaccaata gccggcgggc caaaagaacc aagcccaatg 2100 gccacattgc caataggttg gaaatggaca gcaacacaag ttctgtgagc agtaactcag 2160 aaagtgagac agaagacgaa agagtaggtg aagacacacc attcctgggc atacagaacc 2220 ccctggcagc cagccttgag gtggcccccg ccttccgtct ggctgagagc aggactaacc 2280 cagcaggccg cttctccaca caggaggaat tacaggccag gctgtctagt gtaatcgcta 2340 accaagaccc tattgctgta taaaacctaa ataaacacat agattcacct gtaaaacttt 2400 attttatata ataaagtatt tcaccttaaa ttaaacaatt tattttattt tagcagttct 2460 gcaaatagaa aacaggaaga aaaaaacttt tataaattaa atatatgtat gtaaaaatgt 2520 gttatgtgcc atatgtagca attttttaca gtatttcaaa aacgagaaag atatcaatgg 2580 tgcctttatg ttctgttatg tcgagagcaa gttttataaa gttatggtga tttctttttc 2640 acagtatttc agcaaaacct cccatatatt cagtttctgc tggctttttg tggattgcat 2700 tatgatgttg actggatgta tggtttgcaa ggctagcagc tagctcgcac tcgctctctc 2760 tctctctctc tctctgtctg tctctctgtc tctctctctc tctctctctc tctctgtctc 2820 tctctctctc tctctctctc tctctctctc agcttcccgt agctcccaac ccgtactgtc 2880 ttggactggc acatccatcc aaataccttt ctactttgta tgaagttttc tttgctttcc 2940 caatatgaaa tgagttctct ctactctgtc agccaaaggt ttgcttcact ggactctgag 3000 ataatagtag acccagcagc atgctactat tatgtatagc aggaaactgc accaagtaat 3060 gtccaataat aggaagaaac gatatc 3086 21 782 PRT Rattus norvegicus GGF_1a amino acid sequence 21 Pro Ser Val Gly Ser Val Gln Glu Leu Ala Arg Arg Ala Ala Val 5 10 15 Val Ile Glu Gly Lys Val His Pro Pro Arg Arg Gln Gln Gly Ala 20 25 30 Leu Asp Arg Lys Ala Ala Gly Glu Ala Gly Ala Gly Ala Arg Asp 35 40 45 Gln Pro Val Gln Asp Ser Pro Pro Ser Gln Asp Pro Leu Pro Ala 50 55 60 Val Asn Trp Thr Leu Pro Thr Gly Gly Pro Glu Pro Ser Thr Asp 65 70 75 Gln Pro Gly Asp Pro Ala Pro Tyr Leu Val Lys Val His Gln Val 80 85 90 Trp Ala Val Lys Ala Gly Gly Leu Lys Lys Asp Ser Leu Leu Thr 95 100 105 Val Arg Leu Asp Thr Trp Gly His Pro Ala Phe Pro Ser Cys Gly 110 115 120 Arg Leu Lys Glu Asp Ser Arg Tyr Ile Phe Phe Met Glu Pro Asp 125 130 135 Ala Asn Ser Ser Gly Arg Ala Pro Pro Ala Phe Arg Ala Ser Phe 140 145 150 Pro Pro Leu Glu Thr Gly Arg Asn Leu Lys Lys Glu Val Ser Arg 155 160 165 Val Leu Cys Lys Arg Cys Ala Leu Pro Pro Arg Leu Lys Glu Met 170 175 180 Lys Ser Gln Glu Ser Ala Ala Gly Ser Lys Leu Val Leu Arg Cys 185 190 195 Glu Thr Ser Ser Glu Tyr Ser Ser Leu Arg Phe Lys Trp Phe Lys 200 205 210 Asn Gly Asn Glu Leu Asn Arg Lys Asn Lys Pro Glu Asn Ile Lys 215 220 225 Ile Gln Lys Lys Pro Gly Lys Ser Glu Leu Arg Ile Asn Lys Ala 230 235 240 Ser Leu Ala Asp Ser Gly Glu Tyr Met Cys Lys Val Ile Ser Lys 245 250 255 Leu Gly Asn Asp Ser Ala Ser Ala Asn Ile Thr Ile Val Glu Ser 260 265 270 Asn Glu Phe Ile Thr Gly Met Pro Ala Ser Thr Glu Thr Ala Tyr 275 280 285 Val Ser Ser Glu Ser Pro Ile Arg Ile Ser Val Ser Thr Glu Gly 290 295 300 Ala Asn Thr Ser Ser Ser Thr Ser Thr Ser Thr Thr Gly Thr Ser 305 310 315 His Leu Ile Lys Cys Ala Glu Lys Glu Lys Thr Phe Cys Val Asn 320 325 330 Gly Gly Glu Cys Phe Thr Val Lys Asp Leu Ser Asn Pro Ser Arg 335 340 345 Tyr Leu Cys Lys Cys Pro Asn Glu Phe Thr Gly Asp Arg Cys Gln 350 355 360 Asn Tyr Val Met Ala Ser Phe Tyr Lys His Leu Gly Ile Glu Phe 365 370 375 Met Glu Ala Glu Glu Leu Tyr Gln Lys Arg Val Leu Thr Ile Thr 380 385 390 Gly Ile Cys Ile Ala Leu Leu Val Val Gly Ile Met Cys Val Val 395 400 405 Ala Tyr Cys Lys Thr Lys Lys Gln Arg Gln Lys Leu His Asp Arg 410 415 420 Leu Arg Gln Ser Leu Arg Ser Glu Arg Ser Asn Leu Val Asn Ile 425 430 435 Ala Asn Gly Pro His His Pro Asn Pro Pro Pro Glu Asn Val Gln 440 445 450 Leu Val Asn Gln Tyr Val Ser Lys Asn Val Ile Ser Ser Glu His 455 460 465 Ile Val Glu Arg Glu Val Glu Thr Ser Phe Ser Thr Ser His Tyr 470 475 480 Thr Ser Thr Ala His His Ser Thr Thr Val Thr Gln Thr Pro Ser 485 490 495 His Ser Trp Ser Asn Gly His Thr Glu Ser Val Ile Ser Glu Ser 500 505 510 Asn Ser Val Ile Met Met Ser Ser Val Glu Asn Ser Arg His Ser 515 520 525 Ser Pro Ala Gly Gly Pro Arg Gly Arg Leu His Gly Leu Gly Gly 530 535 540 Pro Arg Asp Asn Ser Phe Leu Arg His Ala Arg Glu Thr Pro Asp 545 550 555 Ser Tyr Arg Asp Ser Pro His Ser Glu Arg Tyr Val Ser Ala Met 560 565 570 Thr Thr Pro Ala Arg Met Ser Pro Val Asp Phe His Thr Pro Ser 575 580 585 Ser Pro Lys Ser Pro Pro Ser Glu Met Ser Pro Pro Val Ser Ser 590 595 600 Met Thr Val Ser Met Pro Ser Val Ala Val Ser Pro Phe Val Glu 605 610 615 Glu Glu Arg Pro Leu Leu Leu Val Thr Pro Pro Arg Leu Arg Glu 620 625 630 Lys Lys Tyr Asp His His Pro Gln Gln Leu Asn Ser Phe His His 635 640 645 Asn Pro Ala His Gln Ser Thr Ser Leu Pro Pro Ser Pro Leu Arg 650 655 660 Ile Val Glu Asp Glu Glu Tyr Glu Thr Thr Gln Glu Tyr Glu Ser 665 670 675 Val Gln Glu Pro Val Lys Lys Val Thr Asn Ser Arg Arg Ala Lys 680 685 690 Arg Thr Lys Pro Asn Gly His Ile Ala Asn Arg Leu Glu Met Asp 695 700 705 Ser Asn Thr Ser Ser Val Ser Ser Asn Ser Glu Ser Glu Thr Glu 710 715 720 Asp Glu Arg Val Gly Glu Asp Thr Pro Phe Leu Gly Ile Gln Asn 725 730 735 Pro Leu Ala Ala Ser Leu Glu Val Ala Pro Ala Phe Arg Leu Ala 740 745 750 Glu Ser Arg Thr Asn Pro Ala Gly Arg Phe Ser Thr Gln Glu Glu 755 760 765 Leu Gln Ala Arg Leu Ser Ser Val Ile Ala Asn Gln Asp Pro Ile 770 775 780 Ala Val 22 952 DNA Rattus norvegicus GGF_2 cDNA sequence 22 ccctctgcct gctgtcaact ggaccctgcc cactgggggc cccgagccca gcaccgatca 60 gcccggggac cccgcgccct atctggtcaa ggtgcaccag gtgtgggctg tgaaagccgg 120 gggtttgaag aaggactcgc tactcaccgt gcgcctggat acctggggcc acccagcctt 180 cccgtcctgc gggcggctca aggaggacag caggtacatc ttcttcatgg agccggatgc 240 caacagcagc ggccgcgcgc cgcccgcctt ccgagcctcg tttcccccac tggagactgg 300 ccgcgacctc aagaaggagg tcagccgggt gttgtgcaag cggtgcgcac tgcctcccag 360 attgaaagaa atgaagagcc aggagtcagc tgcaggctcc aagctagtgc tccggtgcga 420 aaccagctcc gagtactcct cactcagatt caaatggttc aagaatggga acgagctgaa 480 ccgcaaaaat aaaccagaaa acatcaagat acagaagaag ccagggaagt cagagcttcg 540 aattaacaaa gcatccctgg ctgactctgg agagtatatg tgcaaagtga tcagcaagtt 600 aggaaatgac agtgcctctg ccaacatcac cattgttgag tcaaacgagt tcatcactgg 660 catgccagcc tcgactgaga cagcctatgt gtcctcagag tctcccatta gaatctcagt 720 ttcaacagaa ggcgcaaaca cttcttcatc cacatcgaca tccacgactg ggaccagcca 780 tctcataaag tgcgcggaga aggagaaaac tttctgtgtg aatgggggcg agtgcttcac 840 ggtgaaggac ctgtcaaacc cgtcaagata cttgtgcaag tgcccaaatg agtttactgg 900 tgatcgttgc caaaactacg taatggccag cttctacaaa gcggaggaac tc 952 23 317 PRT Rattus norvegicus GGF_2 amino acid sequence 23 Pro Leu Pro Ala Val Asn Trp Thr Leu Pro Thr Gly Gly Pro Glu 5 10 15 Pro Ser Thr Asp Gln Pro Gly Asp Pro Ala Pro Tyr Leu Val Lys 20 25 30 Val His Gln Val Trp Ala Val Lys Ala Gly Gly Leu Lys Lys Asp 35 40 45 Ser Leu Leu Thr Val Arg Leu Asp Thr Trp Gly His Pro Ala Phe 50 55 60 Pro Ser Cys Gly Arg Leu Lys Glu Asp Ser Arg Tyr Ile Phe Phe 65 70 75 Met Glu Pro Asp Ala Asn Ser Ser Gly Arg Ala Pro Pro Ala Phe 80 85 90 Arg Ala Ser Phe Pro Pro Leu Glu Thr Gly Arg Asp Leu Lys Lys 95 100 105 Glu Val Ser Arg Val Leu Cys Lys Arg Cys Ala Leu Pro Pro Arg 110 115 120 Leu Lys Glu Met Lys Ser Gln Glu Ser Ala Ala Gly Ser Lys Leu 125 130 135 Val Leu Arg Cys Glu Thr Ser Ser Glu Tyr Ser Ser Leu Arg Phe 140 145 150 Lys Trp Phe Lys Asn Gly Asn Glu Leu Asn Arg Lys Asn Lys Pro 155 160 165 Glu Asn Ile Lys Ile Gln Lys Lys Pro Gly Lys Ser Glu Leu Arg 170 175 180 Ile Asn Lys Ala Ser Leu Ala Asp Ser Gly Glu Tyr Met Cys Lys 185 190 195 Val Ile Ser Lys Leu Gly Asn Asp Ser Ala Ser Ala Asn Ile Thr 200 205 210 Ile Val Glu Ser Asn Glu Phe Ile Thr Gly Met Pro Ala Ser Thr 215 220 225 Glu Thr Ala Tyr Val Ser Ser Glu Ser Pro Ile Arg Ile Ser Val 230 235 240 Ser Thr Glu Gly Ala Asn Thr Ser Ser Ser Thr Ser Thr Ser Thr 245 250 255 Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu Lys Glu Lys Thr 260 265 270 Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val Lys Asp Leu Ser 275 280 285 Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn Glu Phe Thr Gly 290 295 300 Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe Tyr Lys Ala Glu 305 310 315 Glu Leu 24 1004 DNA Rattus norvegicus GGF_3 cDNA sequence 24 ccctctgcct gctgtcaact ggaccctgcc cactgggggc cccgagccca gcaccgatca 60 gcccggggac cccgcgccct atctggtcaa ggtgcaccag gtgtgggctg tgaaagccgg 120 gggtttgaag aaggactcgc tactcaccgt gcgcctggat acctggggcc acccagcctt 180 cccgtcctgc gggcggctca aggaggacag caggtacatc ttcttcatgg agccggatgc 240 caacagcagc ggccgcgcgc cgcccgcctt ccgagcctcg tttcccccac tggagactgg 300 ccgcaacctc aagaaggagg tcagccgggt gttgtgcaag cggtgcgcac tgcctcccag 360 attgaaagaa atgaagagcc aggagtcagc tgcaggctcc aagctagtgc tccggtgcga 420 aaccagctcc gagtactcct cactcagatt caaatggttc aagaatggga acgagctgaa 480 ccgcaaaaat aaaccagaaa acatcaagat acagaagaag ccagggaagt cagagcttcg 540 aattaacaaa gcatccccgg ctgactctgg agagtatatg tgcaaagtga tcagcaagtt 600 aggaaatgac agtgcctctg ccaacatcac cattgttgag tcaaacgagt tcatcactgg 660 catgccagcc tcgactgaga cagcctatgt gtcctcagag tctcccatta gaatctcagt 720 ttcaacagaa ggcgcaaaca cttcttcatc cacatcaaca tccacgactg ggaccagcca 780 tctcataaag tgtgcggaga aggagaaaac tttctgtgtg aatgggggcg agtgcttcac 840 ggtgaaggac ctgtcaaacc cgtcaagata cttgtgcaag tgcccaaatg agtttactgg 900 tgatcgttgc caaaactacg taatggccag cttctacagt acgtccaccc cctttctgtc 960 tctgcctgag taggagcacg ctcagtcgat gctgctttct tgtt 1004 25 323 PRT Rattus norvegicus GGF_3 amino acid sequence 25 Pro Leu Pro Ala Val Asn Trp Thr Leu Pro Thr Gly Gly Pro Glu 5 10 15 Pro Ser Thr Asp Gln Pro Gly Asp Pro Ala Pro Tyr Leu Val Lys 20 25 30 Val His Gln Val Trp Ala Val Lys Ala Gly Gly Leu Lys Lys Asp 35 40 45 Ser Leu Leu Thr Val Arg Leu Asp Thr Trp Gly His Pro Ala Phe 50 55 60 Pro Ser Cys Gly Arg Leu Lys Glu Asp Ser Arg Tyr Ile Phe Phe 65 70 75 Met Glu Pro Asp Ala Asn Ser Ser Gly Arg Ala Pro Pro Ala Phe 80 85 90 Arg Ala Ser Phe Pro Pro Leu Glu Thr Gly Arg Asn Leu Lys Lys 95 100 105 Glu Val Ser Arg Val Leu Cys Lys Arg Cys Ala Leu Pro Pro Arg 110 115 120 Leu Lys Glu Met Lys Ser Gln Glu Ser Ala Ala Gly Ser Lys Leu 125 130 135 Val Leu Arg Cys Glu Thr Ser Ser Glu Tyr Ser Ser Leu Arg Phe 140 145 150 Lys Trp Phe Lys Asn Gly Asn Glu Leu Asn Arg Lys Asn Lys Pro 155 160 165 Glu Asn Ile Lys Ile Gln Lys Lys Pro Gly Lys Ser Glu Leu Arg 170 175 180 Ile Asn Lys Ala Ser Pro Ala Asp Ser Gly Glu Tyr Met Cys Lys 185 190 195 Val Ile Ser Lys Leu Gly Asn Asp Ser Ala Ser Ala Asn Ile Thr 200 205 210 Ile Val Glu Ser Asn Glu Phe Ile Thr Gly Met Pro Ala Ser Thr 215 220 225 Glu Thr Ala Tyr Val Ser Ser Glu Ser Pro Ile Arg Ile Ser Val 230 235 240 Ser Thr Glu Gly Ala Asn Thr Ser Ser Ser Thr Ser Thr Ser Thr 245 250 255 Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu Lys Glu Lys Thr 260 265 270 Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val Lys Asp Leu Ser 275 280 285 Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn Glu Phe Thr Gly 290 295 300 Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe Tyr Ser Thr Ser 305 310 315 Thr Pro Phe Leu Ser Leu Pro Glu 320 26 1027 DNA Rattus norvegicus GGF_4 cDNA sequence 26 ccctctgcct gctgtcaact ggaccctgcc cactgggggc cccgagccca gcaccgatca 60 gcccggggac cccgcgccct atctggtcaa ggtgcaccag gtgtgggctg tgaaagccgg 120 gggtttgaag aaggactcgc tactcaccgt gcgcctggat acctggggcc acccagcctt 180 cccgtcctgc gggcggctca aggaggacag caggtacatc ttcttcatgg agccggatgc 240 caacagcagc ggccgcgcgc cgcccgcctt ccgagcctcg tttcccccac tggagactgg 300 ccgcaacctc aagaaggagg tcagccgggt gttgtgcaag cggtgcgcac tgcctcccag 360 attgaaagaa atgaagagcc aggagtcagc tgcaggctcc aagctagtgc tccggtgcga 420 aaccagctcc gagtactcct cactcagatt caaatggttc aagaatggga acgagctgaa 480 ccgcaaaaat aaaccagaaa acatcaagat acagaagaag ccagggaagt cagagcttcg 540 aattaacaaa gcatccctgg ctgactctgg agagtatatg tgcaaagtga tcagcaagtt 600 aggaaatgac agtgcctctg ccaacatcac cattgttgag tcaaacgagt tcatcactgg 660 catgccagcc tcgactgaga cagcctatgt gtcctcagag tctcccatta gaatctcagt 720 ttcaacagaa ggcgcaaaca cttcttcatc cacatcaaca tccacgactg ggaccagcca 780 tctcataaag tgtgcggaga aggagaaaac tttctgtgtg aatgggggcg agtgcttcac 840 ggtgaaggac ctgtcaaacc cgtcaagata cttgtgcaag tgcccaaatg agtttactgg 900 tgatcgttgc caaaactacg taatggccag cttctacatg acttctagga ggaaaaggca 960 agaaacagag aagcctctag aaagaaaatt ggatcatagc cttgtgaaag aatcgaaagc 1020 ggaggaa 1027 27 342 PRT Rattus norvegicus GGF_4 amino acid sequence 27 Pro Leu Pro Ala Val Asn Trp Thr Leu Pro Thr Gly Gly Pro Glu 5 10 15 Pro Ser Thr Asp Gln Pro Gly Asp Pro Ala Pro Tyr Leu Val Lys 20 25 30 Val His Gln Val Trp Ala Val Lys Ala Gly Gly Leu Lys Lys Asp 35 40 45 Ser Leu Leu Thr Val Arg Leu Asp Thr Trp Gly His Pro Ala Phe 50 55 60 Pro Ser Cys Gly Arg Leu Lys Glu Asp Ser Arg Tyr Ile Phe Phe 65 70 75 Met Glu Pro Asp Ala Asn Ser Ser Gly Arg Ala Pro Pro Ala Phe 80 85 90 Arg Ala Ser Phe Pro Pro Leu Glu Thr Gly Arg Asn Leu Lys Lys 95 100 105 Glu Val Ser Arg Val Leu Cys Lys Arg Cys Ala Leu Pro Pro Arg 110 115 120 Leu Lys Glu Met Lys Ser Gln Glu Ser Ala Ala Gly Ser Lys Leu 125 130 135 Val Leu Arg Cys Glu Thr Ser Ser Glu Tyr Ser Ser Leu Arg Phe 140 145 150 Lys Trp Phe Lys Asn Gly Asn Glu Leu Asn Arg Lys Asn Lys Pro 155 160 165 Glu Asn Ile Lys Ile Gln Lys Lys Pro Gly Lys Ser Glu Leu Arg 170 175 180 Ile Asn Lys Ala Ser Leu Ala Asp Ser Gly Glu Tyr Met Cys Lys 185 190 195 Val Ile Ser Lys Leu Gly Asn Asp Ser Ala Ser Ala Asn Ile Thr 200 205 210 Ile Val Glu Ser Asn Glu Phe Ile Thr Gly Met Pro Ala Ser Thr 215 220 225 Glu Thr Ala Tyr Val Ser Ser Glu Ser Pro Ile Arg Ile Ser Val 230 235 240 Ser Thr Glu Gly Ala Asn Thr Ser Ser Ser Thr Ser Thr Ser Thr 245 250 255 Thr Gly Thr Ser His Leu Ile Lys Cys Ala Glu Lys Glu Lys Thr 260 265 270 Phe Cys Val Asn Gly Gly Glu Cys Phe Thr Val Lys Asp Leu Ser 275 280 285 Asn Pro Ser Arg Tyr Leu Cys Lys Cys Pro Asn Glu Phe Thr Gly 290 295 300 Asp Arg Cys Gln Asn Tyr Val Met Ala Ser Phe Tyr Met Thr Ser 305 310 315 Arg Arg Lys Arg Gln Glu Thr Glu Lys Pro Leu Glu Arg Lys Leu 320 325 330 Asp His Ser Leu Val Lys Glu Ser Lys Ala Glu Glu 335 340 

What is claimed is:
 1. An isolated splice variant isoform of sensory and motor neuron-derived factor (SMDF) SMDFβ1a protein having an amino acid sequence of SEQ ID No
 2. 2. A method of treating a condition involving nervous system dysfunction, comprising the step of: administering an effective dose of neuregulin SMDFβ1a.
 3. The method of claim 2, wherein said condition is a demyelinating disease.
 4. The method of claim 3, wherein said demyelinating disease is multiple sclerosis.
 5. The method of claim 2, wherein said condition comprises of nerve damage.
 6. The method of claim 5, wherein said nerve damage is selected from the group consisting of spinal cord injury, spinal cord neuropathy, peripheral nerve injury, and peripheral nerve nueropathy. 